C++ GrGLContextInfo类代码示例

void GrGLCaps::initFSAASupport(const GrGLContextInfo& ctxInfo, const GrGLInterface* gli) {

    fMSFBOType = kNone_MSFBOType;
    if (kGL_GrGLStandard != ctxInfo.standard()) {
        // We prefer the EXT/IMG extension over ES3 MSAA because we've observed
        // ES3 driver bugs on at least one device with a tiled GPU (N10).
        if (ctxInfo.hasExtension("GL_EXT_multisampled_render_to_texture")) {
            fMSFBOType = kES_EXT_MsToTexture_MSFBOType;
        } else if (ctxInfo.hasExtension("GL_IMG_multisampled_render_to_texture")) {
            fMSFBOType = kES_IMG_MsToTexture_MSFBOType;
        } else if (ctxInfo.version() >= GR_GL_VER(3,0)) {
            fMSFBOType = GrGLCaps::kES_3_0_MSFBOType;
        } else if (ctxInfo.hasExtension("GL_CHROMIUM_framebuffer_multisample")) {
            // chrome's extension is equivalent to the EXT msaa
            // and fbo_blit extensions.
            fMSFBOType = kDesktop_EXT_MSFBOType;
        } else if (ctxInfo.hasExtension("GL_APPLE_framebuffer_multisample")) {
            fMSFBOType = kES_Apple_MSFBOType;
        }
    } else {
        if ((ctxInfo.version() >= GR_GL_VER(3,0)) ||
            ctxInfo.hasExtension("GL_ARB_framebuffer_object")) {
            fMSFBOType = GrGLCaps::kDesktop_ARB_MSFBOType;
        } else if (ctxInfo.hasExtension("GL_EXT_framebuffer_multisample") &&
                   ctxInfo.hasExtension("GL_EXT_framebuffer_blit")) {
            fMSFBOType = GrGLCaps::kDesktop_EXT_MSFBOType;
        }
    }
}

void GrGLSLCaps::initShaderPrecisionTable(const GrGLContextInfo& ctxInfo,
        const GrGLInterface* intf) {
    if (kGLES_GrGLStandard == ctxInfo.standard() || ctxInfo.version() >= GR_GL_VER(4, 1) ||
            ctxInfo.hasExtension("GL_ARB_ES2_compatibility")) {
        for (int s = 0; s < kGrShaderTypeCount; ++s) {
            if (kGeometry_GrShaderType != s) {
                GrShaderType shaderType = static_cast<GrShaderType>(s);
                GrGLenum glShader = shader_type_to_gl_shader(shaderType);
                PrecisionInfo* first = NULL;
                fShaderPrecisionVaries = false;
                for (int p = 0; p < kGrSLPrecisionCount; ++p) {
                    GrSLPrecision precision = static_cast<GrSLPrecision>(p);
                    GrGLenum glPrecision = precision_to_gl_float_type(precision);
                    GrGLint range[2];
                    GrGLint bits;
                    GR_GL_GetShaderPrecisionFormat(intf, glShader, glPrecision, range, &bits);
                    if (bits) {
                        fFloatPrecisions[s][p].fLogRangeLow = range[0];
                        fFloatPrecisions[s][p].fLogRangeHigh = range[1];
                        fFloatPrecisions[s][p].fBits = bits;
                        if (!first) {
                            first = &fFloatPrecisions[s][p];
                        }
                        else if (!fShaderPrecisionVaries) {
                            fShaderPrecisionVaries = (*first != fFloatPrecisions[s][p]);
                        }
                    }
                }
            }
        }
    }
    else {
        // We're on a desktop GL that doesn't have precision info. Assume they're all 32bit float.
        fShaderPrecisionVaries = false;
        for (int s = 0; s < kGrShaderTypeCount; ++s) {
            if (kGeometry_GrShaderType != s) {
                for (int p = 0; p < kGrSLPrecisionCount; ++p) {
                    fFloatPrecisions[s][p].fLogRangeLow = 127;
                    fFloatPrecisions[s][p].fLogRangeHigh = 127;
                    fFloatPrecisions[s][p].fBits = 23;
                }
            }
        }
    }
    // GetShaderPrecisionFormat doesn't accept GL_GEOMETRY_SHADER as a shader type. Assume they're
    // the same as the vertex shader. Only fragment shaders were ever allowed to omit support for
    // highp. GS was added after GetShaderPrecisionFormat was added to the list of features that
    // are recommended against.
    if (fGeometryShaderSupport) {
        for (int p = 0; p < kGrSLPrecisionCount; ++p) {
            fFloatPrecisions[kGeometry_GrShaderType][p] = fFloatPrecisions[kVertex_GrShaderType][p];
        }
    }
}

void GrGLCaps::initFSAASupport(const GrGLContextInfo& ctxInfo, const GrGLInterface* gli) {

    fMSFBOType = kNone_MSFBOType;
    if (kDesktop_GrGLBinding != ctxInfo.binding()) {
       if (ctxInfo.hasExtension("GL_CHROMIUM_framebuffer_multisample")) {
           // chrome's extension is equivalent to the EXT msaa
           // and fbo_blit extensions.
           fMSFBOType = kDesktopEXT_MSFBOType;
       } else if (ctxInfo.hasExtension("GL_APPLE_framebuffer_multisample")) {
           fMSFBOType = kAppleES_MSFBOType;
       } else if (ctxInfo.hasExtension("GL_IMG_multisampled_render_to_texture")) {
           fMSFBOType = kImaginationES_MSFBOType;
       }
    } else {
        if ((ctxInfo.version() >= GR_GL_VER(3,0)) ||
            ctxInfo.hasExtension("GL_ARB_framebuffer_object")) {
            fMSFBOType = GrGLCaps::kDesktopARB_MSFBOType;
        } else if (ctxInfo.hasExtension("GL_EXT_framebuffer_multisample") &&
                   ctxInfo.hasExtension("GL_EXT_framebuffer_blit")) {
            fMSFBOType = GrGLCaps::kDesktopEXT_MSFBOType;
        }
        // TODO: We could populate fMSAACoverageModes using GetInternalformativ
        // on GL 4.2+. It's format-specific, though. See also
        // http://code.google.com/p/skia/issues/detail?id=470 about using actual
        // rather than requested sample counts in cache key.
        if (ctxInfo.hasExtension("GL_NV_framebuffer_multisample_coverage")) {
            fCoverageAAType = kNVDesktop_CoverageAAType;
            GrGLint count;
            GR_GL_GetIntegerv(gli,
                              GR_GL_MAX_MULTISAMPLE_COVERAGE_MODES,
                              &count);
            fMSAACoverageModes.setCount(count);
            GR_GL_GetIntegerv(gli,
                              GR_GL_MULTISAMPLE_COVERAGE_MODES,
                              (int*)&fMSAACoverageModes[0]);
            // The NV driver seems to return the modes already sorted but the
            // spec doesn't require this. So we sort.
            qsort(&fMSAACoverageModes[0],
                    count,
                    sizeof(MSAACoverageMode),
                    SkCastForQSort(coverage_mode_compare));
        }
    }
}

void GrGLCaps::initStencilFormats(const GrGLContextInfo& ctxInfo) {

    // Build up list of legal stencil formats (though perhaps not supported on
    // the particular gpu/driver) from most preferred to least.

    // these consts are in order of most preferred to least preferred
    // we don't bother with GL_STENCIL_INDEX1 or GL_DEPTH32F_STENCIL8

    static const StencilFormat
                  // internal Format      stencil bits      total bits        packed?
        gS8    = {GR_GL_STENCIL_INDEX8,   8,                8,                false},
        gS16   = {GR_GL_STENCIL_INDEX16,  16,               16,               false},
        gD24S8 = {GR_GL_DEPTH24_STENCIL8, 8,                32,               true },
        gS4    = {GR_GL_STENCIL_INDEX4,   4,                4,                false},
    //  gS     = {GR_GL_STENCIL_INDEX,    kUnknownBitCount, kUnknownBitCount, false},
        gDS    = {GR_GL_DEPTH_STENCIL,    kUnknownBitCount, kUnknownBitCount, true };

    if (kGL_GrGLStandard == ctxInfo.standard()) {
        bool supportsPackedDS =
            ctxInfo.version() >= GR_GL_VER(3,0) ||
            ctxInfo.hasExtension("GL_EXT_packed_depth_stencil") ||
            ctxInfo.hasExtension("GL_ARB_framebuffer_object");

        // S1 thru S16 formats are in GL 3.0+, EXT_FBO, and ARB_FBO since we
        // require FBO support we can expect these are legal formats and don't
        // check. These also all support the unsized GL_STENCIL_INDEX.
        fStencilFormats.push_back() = gS8;
        fStencilFormats.push_back() = gS16;
        if (supportsPackedDS) {
            fStencilFormats.push_back() = gD24S8;
        }
        fStencilFormats.push_back() = gS4;
        if (supportsPackedDS) {
            fStencilFormats.push_back() = gDS;
        }
    } else {
        // ES2 has STENCIL_INDEX8 without extensions but requires extensions
        // for other formats.
        // ES doesn't support using the unsized format.

        fStencilFormats.push_back() = gS8;
        //fStencilFormats.push_back() = gS16;
        if (ctxInfo.version() >= GR_GL_VER(3,0) ||
            ctxInfo.hasExtension("GL_OES_packed_depth_stencil")) {
            fStencilFormats.push_back() = gD24S8;
        }
        if (ctxInfo.hasExtension("GL_OES_stencil4")) {
            fStencilFormats.push_back() = gS4;
        }
    }
    SkASSERT(0 == fStencilVerifiedColorConfigs.count());
    fStencilVerifiedColorConfigs.push_back_n(fStencilFormats.count());
}

void GrGLCaps::initFSAASupport(const GrGLContextInfo& ctxInfo) {

    fMSFBOType = kNone_MSFBOType;
    if (kDesktop_GrGLBinding != ctxInfo.binding()) {
       if (ctxInfo.hasExtension("GL_CHROMIUM_framebuffer_multisample")) {
           // chrome's extension is equivalent to the EXT msaa
           // and fbo_blit extensions.
           fMSFBOType = kDesktopEXT_MSFBOType;
       } else if (ctxInfo.hasExtension("GL_APPLE_framebuffer_multisample")) {
            fMSFBOType = kAppleES_MSFBOType;
        }
    } else {
        if ((ctxInfo.version() >= GR_GL_VER(3,0)) ||
            ctxInfo.hasExtension("GL_ARB_framebuffer_object")) {
            fMSFBOType = GrGLCaps::kDesktopARB_MSFBOType;
        } else if (ctxInfo.hasExtension("GL_EXT_framebuffer_multisample") &&
                   ctxInfo.hasExtension("GL_EXT_framebuffer_blit")) {
            fMSFBOType = GrGLCaps::kDesktopEXT_MSFBOType;
        }
    }
}

void GrGLCaps::init(const GrGLContextInfo& ctxInfo) {

    this->reset();
    if (!ctxInfo.isInitialized()) {
        return;
    }

    const GrGLInterface* gli = ctxInfo.interface();
    GrGLBinding binding = ctxInfo.binding();
    GrGLVersion version = ctxInfo.version();

    if (kES2_GrGLBinding == binding) {
        GR_GL_GetIntegerv(gli, GR_GL_MAX_FRAGMENT_UNIFORM_VECTORS,
                          &fMaxFragmentUniformVectors);
    } else {
        GrAssert(kDesktop_GrGLBinding == binding);
        GrGLint max;
        GR_GL_GetIntegerv(gli, GR_GL_MAX_FRAGMENT_UNIFORM_COMPONENTS, &max);
        fMaxFragmentUniformVectors = max / 4;
    }

    if (kDesktop_GrGLBinding == binding) {
        fRGBA8RenderbufferSupport = true;
    } else {
        fRGBA8RenderbufferSupport = ctxInfo.hasExtension("GL_OES_rgb8_rgba8") ||
                                    ctxInfo.hasExtension("GL_ARM_rgba8");
    }

    if (kDesktop_GrGLBinding == binding) {
        fBGRAFormatSupport = version >= GR_GL_VER(1,2) ||
                             ctxInfo.hasExtension("GL_EXT_bgra");
    } else {
        bool hasBGRAExt = false;
        if (ctxInfo.hasExtension("GL_APPLE_texture_format_BGRA8888")) {
            fBGRAFormatSupport = true;
        } else if (ctxInfo.hasExtension("GL_EXT_texture_format_BGRA8888")) {
            fBGRAFormatSupport = true;
            fBGRAIsInternalFormat = true;
        }
        GrAssert(fBGRAFormatSupport ||
                 kSkia8888_PM_GrPixelConfig != kBGRA_8888_PM_GrPixelConfig);
    }

    if (kDesktop_GrGLBinding == binding) {
        fTextureSwizzleSupport = version >= GR_GL_VER(3,3) ||
                                 ctxInfo.hasExtension("GL_ARB_texture_swizzle");
    } else {
        fTextureSwizzleSupport = false;
    }

    if (kDesktop_GrGLBinding == binding) {
        fUnpackRowLengthSupport = true;
        fUnpackFlipYSupport = false;
        fPackRowLengthSupport = true;
        fPackFlipYSupport = false;
    } else {
        fUnpackRowLengthSupport =ctxInfo.hasExtension("GL_EXT_unpack_subimage");
        fUnpackFlipYSupport = ctxInfo.hasExtension("GL_CHROMIUM_flipy");
        // no extension for pack row length
        fPackRowLengthSupport = false;
        fPackFlipYSupport =
            ctxInfo.hasExtension("GL_ANGLE_pack_reverse_row_order");
    }

    fTextureUsageSupport = (kES2_GrGLBinding == binding) &&
                            ctxInfo.hasExtension("GL_ANGLE_texture_usage");

    // Tex storage is in desktop 4.2 and can be an extension to desktop or ES.
    fTexStorageSupport = (kDesktop_GrGLBinding == binding &&
                          version >= GR_GL_VER(4,2)) ||
                         ctxInfo.hasExtension("GL_ARB_texture_storage") ||
                         ctxInfo.hasExtension("GL_EXT_texture_storage");

    // ARB_texture_rg is part of OpenGL 3.0
    if (kDesktop_GrGLBinding == binding) {
        fTextureRedSupport = version >= GR_GL_VER(3,0) ||
                             ctxInfo.hasExtension("GL_ARB_texture_rg");
    } else {
        fTextureRedSupport = ctxInfo.hasExtension("GL_ARB_texture_rg");
    }

    this->initFSAASupport(ctxInfo);
    this->initStencilFormats(ctxInfo);
}

bool GrGLCaps::init(const GrGLContextInfo& ctxInfo, const GrGLInterface* gli) {

    this->reset();
    if (!ctxInfo.isInitialized()) {
        return false;
    }

    GrGLStandard standard = ctxInfo.standard();
    GrGLVersion version = ctxInfo.version();

    /**************************************************************************
     * Caps specific to GrGLCaps
     **************************************************************************/

    if (kGLES_GrGLStandard == standard) {
        GR_GL_GetIntegerv(gli, GR_GL_MAX_FRAGMENT_UNIFORM_VECTORS,
                          &fMaxFragmentUniformVectors);
    } else {
        SkASSERT(kGL_GrGLStandard == standard);
        GrGLint max;
        GR_GL_GetIntegerv(gli, GR_GL_MAX_FRAGMENT_UNIFORM_COMPONENTS, &max);
        fMaxFragmentUniformVectors = max / 4;
        if (version >= GR_GL_VER(3, 2)) {
            GrGLint profileMask;
            GR_GL_GetIntegerv(gli, GR_GL_CONTEXT_PROFILE_MASK, &profileMask);
            fIsCoreProfile = SkToBool(profileMask & GR_GL_CONTEXT_CORE_PROFILE_BIT);
        }
        if (!fIsCoreProfile) {
            GR_GL_GetIntegerv(gli, GR_GL_MAX_TEXTURE_COORDS, &fMaxFixedFunctionTextureCoords);
            // Sanity check
            SkASSERT(fMaxFixedFunctionTextureCoords > 0 && fMaxFixedFunctionTextureCoords < 128);
        }
    }
    GR_GL_GetIntegerv(gli, GR_GL_MAX_VERTEX_ATTRIBS, &fMaxVertexAttributes);
    GR_GL_GetIntegerv(gli, GR_GL_MAX_TEXTURE_IMAGE_UNITS, &fMaxFragmentTextureUnits);

    if (kGL_GrGLStandard == standard) {
        fRGBA8RenderbufferSupport = true;
    } else {
        fRGBA8RenderbufferSupport = version >= GR_GL_VER(3,0) ||
                                    ctxInfo.hasExtension("GL_OES_rgb8_rgba8") ||
                                    ctxInfo.hasExtension("GL_ARM_rgba8");
    }

    if (kGL_GrGLStandard == standard) {
        fTextureSwizzleSupport = version >= GR_GL_VER(3,3) ||
                                 ctxInfo.hasExtension("GL_ARB_texture_swizzle");
    } else {
        fTextureSwizzleSupport = version >= GR_GL_VER(3,0);
    }

    if (kGL_GrGLStandard == standard) {
        fUnpackRowLengthSupport = true;
        fUnpackFlipYSupport = false;
        fPackRowLengthSupport = true;
        fPackFlipYSupport = false;
    } else {
        fUnpackRowLengthSupport = version >= GR_GL_VER(3,0) ||
                                  ctxInfo.hasExtension("GL_EXT_unpack_subimage");
        fUnpackFlipYSupport = ctxInfo.hasExtension("GL_CHROMIUM_flipy");
        fPackRowLengthSupport = version >= GR_GL_VER(3,0) ||
                                ctxInfo.hasExtension("GL_NV_pack_subimage");
        fPackFlipYSupport =
            ctxInfo.hasExtension("GL_ANGLE_pack_reverse_row_order");
    }

    fTextureUsageSupport = (kGLES_GrGLStandard == standard) &&
                            ctxInfo.hasExtension("GL_ANGLE_texture_usage");

    if (kGL_GrGLStandard == standard) {
        // The EXT version can apply to either GL or GLES.
        fTexStorageSupport = version >= GR_GL_VER(4,2) ||
                             ctxInfo.hasExtension("GL_ARB_texture_storage") ||
                             ctxInfo.hasExtension("GL_EXT_texture_storage");
    } else {
        // Qualcomm Adreno drivers appear to have issues with texture storage.
        fTexStorageSupport = (version >= GR_GL_VER(3,0) &&
                              kQualcomm_GrGLVendor != ctxInfo.vendor()) ||
                             ctxInfo.hasExtension("GL_EXT_texture_storage");
    }

    // ARB_texture_rg is part of OpenGL 3.0, but mesa doesn't support it if
    // it doesn't have ARB_texture_rg extension.
    if (kGL_GrGLStandard == standard) {
        if (ctxInfo.isMesa()) {
            fTextureRedSupport = ctxInfo.hasExtension("GL_ARB_texture_rg");
        } else {
            fTextureRedSupport = version >= GR_GL_VER(3,0) ||
                                 ctxInfo.hasExtension("GL_ARB_texture_rg");
        }
    } else {
        fTextureRedSupport =  version >= GR_GL_VER(3,0) ||
                              ctxInfo.hasExtension("GL_EXT_texture_rg");
    }

    fImagingSupport = kGL_GrGLStandard == standard &&
                      ctxInfo.hasExtension("GL_ARB_imaging");

    // ES 2 only guarantees RGBA/uchar + one other format/type combo for
    // ReadPixels. The other format has to checked at run-time since it
//.........这里部分代码省略.........

void GrGLCaps::initConfigTexturableTable(const GrGLContextInfo& ctxInfo, const GrGLInterface* gli) {
    GrGLStandard standard = ctxInfo.standard();
    GrGLVersion version = ctxInfo.version();

    // Base texture support
    fConfigTextureSupport[kAlpha_8_GrPixelConfig] = true;
    fConfigTextureSupport[kRGB_565_GrPixelConfig] = true;
    fConfigTextureSupport[kRGBA_4444_GrPixelConfig] = true;
    fConfigTextureSupport[kRGBA_8888_GrPixelConfig] = true;

    // Check for 8-bit palette..
    GrGLint numFormats;
    GR_GL_GetIntegerv(gli, GR_GL_NUM_COMPRESSED_TEXTURE_FORMATS, &numFormats);
    if (numFormats) {
        SkAutoSTMalloc<10, GrGLint> formats(numFormats);
        GR_GL_GetIntegerv(gli, GR_GL_COMPRESSED_TEXTURE_FORMATS, formats);
        for (int i = 0; i < numFormats; ++i) {
            if (GR_GL_PALETTE8_RGBA8 == formats[i]) {
                fConfigTextureSupport[kIndex_8_GrPixelConfig] = true;
                break;
            }
        }
    }

    // Check for BGRA
    if (kGL_GrGLStandard == standard) {
        fConfigTextureSupport[kBGRA_8888_GrPixelConfig] =
            version >= GR_GL_VER(1,2) || ctxInfo.hasExtension("GL_EXT_bgra");
    } else {
        if (ctxInfo.hasExtension("GL_APPLE_texture_format_BGRA8888")) {
            fConfigTextureSupport[kBGRA_8888_GrPixelConfig] = true;
        } else if (ctxInfo.hasExtension("GL_EXT_texture_format_BGRA8888")) {
            fConfigTextureSupport[kBGRA_8888_GrPixelConfig] = true;
            fBGRAIsInternalFormat = true;
        }
        SkASSERT(fConfigTextureSupport[kBGRA_8888_GrPixelConfig] ||
                 kSkia8888_GrPixelConfig != kBGRA_8888_GrPixelConfig);
    }

    // Compressed texture support

    // glCompressedTexImage2D is available on all OpenGL ES devices...
    // however, it is only available on standard OpenGL after version 1.3
    bool hasCompressTex2D = (kGL_GrGLStandard != standard || version >= GR_GL_VER(1, 3));

    // Check for ETC1
    bool hasETC1 = false;

    // First check version for support
    if (kGL_GrGLStandard == standard) {
        hasETC1 = hasCompressTex2D &&
            (version >= GR_GL_VER(4, 3) || 
             ctxInfo.hasExtension("GL_ARB_ES3_compatibility"));
    } else {
        hasETC1 = hasCompressTex2D &&
            (version >= GR_GL_VER(3, 0) ||
             ctxInfo.hasExtension("GL_OES_compressed_ETC1_RGB8_texture") ||
             // ETC2 is a superset of ETC1, so we can just check for that, too.
             (ctxInfo.hasExtension("GL_OES_compressed_ETC2_RGB8_texture") &&
              ctxInfo.hasExtension("GL_OES_compressed_ETC2_RGBA8_texture")));
    }
    fConfigTextureSupport[kETC1_GrPixelConfig] = hasETC1;

    // Check for LATC under its various forms
    LATCAlias alias = kLATC_LATCAlias;
    bool hasLATC = hasCompressTex2D &&
        (ctxInfo.hasExtension("GL_EXT_texture_compression_latc") ||
         ctxInfo.hasExtension("GL_NV_texture_compression_latc"));

    // Check for RGTC
    if (!hasLATC) {
        // If we're using OpenGL 3.0 or later, then we have RGTC, an identical compression format.
        if (kGL_GrGLStandard == standard) {
            hasLATC = version >= GR_GL_VER(3, 0);
        }

        if (!hasLATC) {
            hasLATC =
                ctxInfo.hasExtension("GL_EXT_texture_compression_rgtc") ||
                ctxInfo.hasExtension("GL_ARB_texture_compression_rgtc");
        }

        if (hasLATC) {
            alias = kRGTC_LATCAlias;
        }
    }

    // Check for 3DC
    if (!hasLATC) {
        hasLATC = ctxInfo.hasExtension("GL_AMD_compressed_3DC_texture");
        if (hasLATC) {
            alias = k3DC_LATCAlias;
        }
    }

    fConfigTextureSupport[kLATC_GrPixelConfig] = hasLATC;
    fLATCAlias = alias;
}

void GrGLCaps::initConfigRenderableTable(const GrGLContextInfo& ctxInfo) {

    // 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

    // ES 3.0
    // Same as ES 2.0 except R8 and RGBA8 are supported without extensions (the functions called
    // below already account for this).

    GrGLStandard standard = ctxInfo.standard();

    enum {
        kNo_MSAA = 0,
        kYes_MSAA = 1,
    };

    if (kGL_GrGLStandard == standard) {
        // Post 3.0 we will get R8
        // Prior to 3.0 we will get ALPHA8 (with GL_ARB_framebuffer_object)
        if (ctxInfo.version() >= GR_GL_VER(3,0) ||
            ctxInfo.hasExtension("GL_ARB_framebuffer_object")) {
            fConfigRenderSupport[kAlpha_8_GrPixelConfig][kNo_MSAA] = true;
            fConfigRenderSupport[kAlpha_8_GrPixelConfig][kYes_MSAA] = true;
        }
    } else {
        // On ES we can only hope for R8
        fConfigRenderSupport[kAlpha_8_GrPixelConfig][kNo_MSAA] = fTextureRedSupport;
        fConfigRenderSupport[kAlpha_8_GrPixelConfig][kYes_MSAA] = fTextureRedSupport;
    }

    if (kGL_GrGLStandard != standard) {
        // only available in ES
        fConfigRenderSupport[kRGB_565_GrPixelConfig][kNo_MSAA] = true;
        fConfigRenderSupport[kRGB_565_GrPixelConfig][kYes_MSAA] = true;
    }

    // we no longer support 444 as a render target
    fConfigRenderSupport[kRGBA_4444_GrPixelConfig][kNo_MSAA]  = false;
    fConfigRenderSupport[kRGBA_4444_GrPixelConfig][kYes_MSAA]  = false;

    if (this->fRGBA8RenderbufferSupport) {
        fConfigRenderSupport[kRGBA_8888_GrPixelConfig][kNo_MSAA]  = true;
        fConfigRenderSupport[kRGBA_8888_GrPixelConfig][kYes_MSAA]  = true;
    }

    if (this->isConfigTexturable(kBGRA_8888_GrPixelConfig)) {
        fConfigRenderSupport[kBGRA_8888_GrPixelConfig][kNo_MSAA]  = true;
        // The GL_EXT_texture_format_BGRA8888 extension does not add BGRA to the list of
        // configs that are color-renderable and can be passed to glRenderBufferStorageMultisample.
        // Chromium may have an extension to allow BGRA renderbuffers to work on desktop platforms.
        if (ctxInfo.hasExtension("GL_CHROMIUM_renderbuffer_format_BGRA8888")) {
            fConfigRenderSupport[kBGRA_8888_GrPixelConfig][kYes_MSAA] = true;
        } else {
            fConfigRenderSupport[kBGRA_8888_GrPixelConfig][kYes_MSAA] =
                !fBGRAIsInternalFormat || !this->usesMSAARenderBuffers();
        }
    }

    // If we don't support MSAA then undo any places above where we set a config as renderable with
    // msaa.
    if (kNone_MSFBOType == fMSFBOType) {
        for (int i = 0; i < kGrPixelConfigCnt; ++i) {
            fConfigRenderSupport[i][kYes_MSAA] = false;
        }
    }
}

void GrGLCaps::initConfigTexturableTable(const GrGLContextInfo& ctxInfo, const GrGLInterface* gli) {
    GrGLStandard standard = ctxInfo.standard();
    GrGLVersion version = ctxInfo.version();

    // Base texture support
    fConfigTextureSupport[kAlpha_8_GrPixelConfig] = true;
    fConfigTextureSupport[kRGB_565_GrPixelConfig] = true;
    fConfigTextureSupport[kRGBA_4444_GrPixelConfig] = true;
    fConfigTextureSupport[kRGBA_8888_GrPixelConfig] = true;

    // Check for 8-bit palette..
    GrGLint numFormats;
    GR_GL_GetIntegerv(gli, GR_GL_NUM_COMPRESSED_TEXTURE_FORMATS, &numFormats);
    if (numFormats) {
        SkAutoSTMalloc<10, GrGLint> formats(numFormats);
        GR_GL_GetIntegerv(gli, GR_GL_COMPRESSED_TEXTURE_FORMATS, formats);
        for (int i = 0; i < numFormats; ++i) {
            if (GR_GL_PALETTE8_RGBA8 == formats[i]) {
                fConfigTextureSupport[kIndex_8_GrPixelConfig] = true;
                break;
            }
        }
    }

    // Check for BGRA
    if (kGL_GrGLStandard == standard) {
        fConfigTextureSupport[kBGRA_8888_GrPixelConfig] =
            version >= GR_GL_VER(1,2) || ctxInfo.hasExtension("GL_EXT_bgra");
    } else {
        if (ctxInfo.hasExtension("GL_APPLE_texture_format_BGRA8888")) {
            fConfigTextureSupport[kBGRA_8888_GrPixelConfig] = true;
        } else if (ctxInfo.hasExtension("GL_EXT_texture_format_BGRA8888")) {
            fConfigTextureSupport[kBGRA_8888_GrPixelConfig] = true;
            fBGRAIsInternalFormat = true;
        }
        SkASSERT(fConfigTextureSupport[kBGRA_8888_GrPixelConfig] ||
                 kSkia8888_GrPixelConfig != kBGRA_8888_GrPixelConfig);
    }

    // Check for sRGBA
    if (kGL_GrGLStandard == standard) {
        fConfigTextureSupport[kSRGBA_8888_GrPixelConfig] =
            (version >= GR_GL_VER(3,0) || ctxInfo.hasExtension("GL_EXT_texture_sRGB"));
    } else {
        fConfigTextureSupport[kSRGBA_8888_GrPixelConfig] =
            (version >= GR_GL_VER(3,0) || ctxInfo.hasExtension("GL_EXT_sRGB"));
    }
    
    // Compressed texture support

    // glCompressedTexImage2D is available on all OpenGL ES devices...
    // however, it is only available on standard OpenGL after version 1.3
    bool hasCompressTex2D = (kGL_GrGLStandard != standard || version >= GR_GL_VER(1, 3));

    fCompressedTexSubImageSupport =
        hasCompressTex2D && (gli->fFunctions.fCompressedTexSubImage2D);

    // Check for ETC1
    bool hasETC1 = false;

    // First check version for support
    if (kGL_GrGLStandard == standard) {
        hasETC1 = hasCompressTex2D &&
            (version >= GR_GL_VER(4, 3) ||
             ctxInfo.hasExtension("GL_ARB_ES3_compatibility"));
    } else {
        hasETC1 = hasCompressTex2D &&
            (version >= GR_GL_VER(3, 0) ||
             ctxInfo.hasExtension("GL_OES_compressed_ETC1_RGB8_texture") ||
             // ETC2 is a superset of ETC1, so we can just check for that, too.
             (ctxInfo.hasExtension("GL_OES_compressed_ETC2_RGB8_texture") &&
              ctxInfo.hasExtension("GL_OES_compressed_ETC2_RGBA8_texture")));
    }
    fConfigTextureSupport[kETC1_GrPixelConfig] = hasETC1;

    // Check for LATC under its various forms
    LATCAlias alias = kLATC_LATCAlias;
    bool hasLATC = hasCompressTex2D &&
        (ctxInfo.hasExtension("GL_EXT_texture_compression_latc") ||
         ctxInfo.hasExtension("GL_NV_texture_compression_latc"));

    // Check for RGTC
    if (!hasLATC) {
        // If we're using OpenGL 3.0 or later, then we have RGTC, an identical compression format.
        if (kGL_GrGLStandard == standard) {
            hasLATC = version >= GR_GL_VER(3, 0);
        }

        if (!hasLATC) {
            hasLATC =
                ctxInfo.hasExtension("GL_EXT_texture_compression_rgtc") ||
                ctxInfo.hasExtension("GL_ARB_texture_compression_rgtc");
        }

        if (hasLATC) {
            alias = kRGTC_LATCAlias;
        }
    }

    // Check for 3DC
//.........这里部分代码省略.........

bool GrGLSLCaps::init(const GrGLContextInfo& ctxInfo,
                      const GrGLInterface* gli,
                      const GrGLCaps& glCaps) {
    this->reset();
    if (!ctxInfo.isInitialized()) {
        return false;
    }

    GrGLStandard standard = ctxInfo.standard();
    GrGLVersion version = ctxInfo.version();

    /**************************************************************************
    * Caps specific to GrGLSLCaps
    **************************************************************************/

    if (kGLES_GrGLStandard == standard) {
        if (ctxInfo.hasExtension("GL_EXT_shader_framebuffer_fetch")) {
            fFBFetchNeedsCustomOutput = (version >= GR_GL_VER(3, 0));
            fFBFetchSupport = true;
            fFBFetchColorName = "gl_LastFragData[0]";
            fFBFetchExtensionString = "GL_EXT_shader_framebuffer_fetch";
        }
        else if (ctxInfo.hasExtension("GL_NV_shader_framebuffer_fetch")) {
            // Actually, we haven't seen an ES3.0 device with this extension yet, so we don't know
            fFBFetchNeedsCustomOutput = false;
            fFBFetchSupport = true;
            fFBFetchColorName = "gl_LastFragData[0]";
            fFBFetchExtensionString = "GL_NV_shader_framebuffer_fetch";
        }
        else if (ctxInfo.hasExtension("GL_ARM_shader_framebuffer_fetch")) {
            // The arm extension also requires an additional flag which we will set onResetContext
            fFBFetchNeedsCustomOutput = false;
            fFBFetchSupport = true;
            fFBFetchColorName = "gl_LastFragColorARM";
            fFBFetchExtensionString = "GL_ARM_shader_framebuffer_fetch";
        }
    }

    // Adreno GPUs have a tendency to drop tiles when there is a divide-by-zero in a shader
    fDropsTileOnZeroDivide = kQualcomm_GrGLVendor == ctxInfo.vendor();

    /**************************************************************************
    * GrShaderCaps fields
    **************************************************************************/

    fPathRenderingSupport = ctxInfo.hasExtension("GL_NV_path_rendering");

    if (fPathRenderingSupport) {
        if (kGL_GrGLStandard == standard) {
            // We only support v1.3+ of GL_NV_path_rendering which allows us to
            // set individual fragment inputs with ProgramPathFragmentInputGen. The API
            // additions are detected by checking the existence of the function.
            fPathRenderingSupport = ctxInfo.hasExtension("GL_EXT_direct_state_access") &&
                                    ((ctxInfo.version() >= GR_GL_VER(4, 3) ||
                                      ctxInfo.hasExtension("GL_ARB_program_interface_query")) &&
                                     gli->fFunctions.fProgramPathFragmentInputGen);
        }
        else {
            fPathRenderingSupport = ctxInfo.version() >= GR_GL_VER(3, 1);
        }
    }

    // For now these two are equivalent but we could have dst read in shader via some other method
    fDstReadInShaderSupport = fFBFetchSupport;

    // Enable supported shader-related caps
    if (kGL_GrGLStandard == standard) {
        fDualSourceBlendingSupport = ctxInfo.version() >= GR_GL_VER(3, 3) ||
                                     ctxInfo.hasExtension("GL_ARB_blend_func_extended");
        fShaderDerivativeSupport = true;
        // we don't support GL_ARB_geometry_shader4, just GL 3.2+ GS
        fGeometryShaderSupport = ctxInfo.version() >= GR_GL_VER(3, 2) &&
                                 ctxInfo.glslGeneration() >= k150_GrGLSLGeneration;
    }
    else {
        fShaderDerivativeSupport = ctxInfo.version() >= GR_GL_VER(3, 0) ||
                                   ctxInfo.hasExtension("GL_OES_standard_derivatives");
    }

    if (glCaps.advancedBlendEquationSupport()) {
        bool coherent = glCaps.advancedCoherentBlendEquationSupport();
        if (ctxInfo.hasExtension(coherent ? "GL_NV_blend_equation_advanced_coherent"
                                 : "GL_NV_blend_equation_advanced")) {
            fAdvBlendEqInteraction = kAutomatic_AdvBlendEqInteraction;
        } else {
            fAdvBlendEqInteraction = kGeneralEnable_AdvBlendEqInteraction;
            // TODO: Use the following on any platform where "blend_support_all_equations" is slow.
            //fAdvBlendEqInteraction = kSpecificEnables_AdvBlendEqInteraction;
        }
    }

    this->initShaderPrecisionTable(ctxInfo, gli);

    return true;
}

void GrGLCaps::init(const GrGLContextInfo& ctxInfo) {

    this->reset();
    if (!ctxInfo.isInitialized()) {
        return;
    }

    const GrGLInterface* gli = ctxInfo.interface();
    GrGLBinding binding = ctxInfo.binding();
    GrGLVersion version = ctxInfo.version();

    if (kES2_GrGLBinding == binding) {
        GR_GL_GetIntegerv(gli, GR_GL_MAX_FRAGMENT_UNIFORM_VECTORS,
                          &fMaxFragmentUniformVectors);
    } else {
        GrAssert(kDesktop_GrGLBinding == binding);
        GrGLint max;
        GR_GL_GetIntegerv(gli, GR_GL_MAX_FRAGMENT_UNIFORM_COMPONENTS, &max);
        fMaxFragmentUniformVectors = max / 4;
    }
    GR_GL_GetIntegerv(gli, GR_GL_MAX_VERTEX_ATTRIBS, &fMaxVertexAttributes);

    if (kDesktop_GrGLBinding == binding) {
        fRGBA8RenderbufferSupport = true;
    } else {
        fRGBA8RenderbufferSupport = ctxInfo.hasExtension("GL_OES_rgb8_rgba8") ||
                                    ctxInfo.hasExtension("GL_ARM_rgba8");
    }

    if (kDesktop_GrGLBinding == binding) {
        fBGRAFormatSupport = version >= GR_GL_VER(1,2) ||
                             ctxInfo.hasExtension("GL_EXT_bgra");
    } else {
        if (ctxInfo.hasExtension("GL_APPLE_texture_format_BGRA8888")) {
            fBGRAFormatSupport = true;
        } else if (ctxInfo.hasExtension("GL_EXT_texture_format_BGRA8888")) {
            fBGRAFormatSupport = true;
            fBGRAIsInternalFormat = true;
        }
        GrAssert(fBGRAFormatSupport ||
                 kSkia8888_GrPixelConfig != kBGRA_8888_GrPixelConfig);
    }

    if (kDesktop_GrGLBinding == binding) {
        fTextureSwizzleSupport = version >= GR_GL_VER(3,3) ||
                                 ctxInfo.hasExtension("GL_ARB_texture_swizzle");
    } else {
        fTextureSwizzleSupport = false;
    }

    if (kDesktop_GrGLBinding == binding) {
        fUnpackRowLengthSupport = true;
        fUnpackFlipYSupport = false;
        fPackRowLengthSupport = true;
        fPackFlipYSupport = false;
    } else {
        fUnpackRowLengthSupport =ctxInfo.hasExtension("GL_EXT_unpack_subimage");
        fUnpackFlipYSupport = ctxInfo.hasExtension("GL_CHROMIUM_flipy");
        // no extension for pack row length
        fPackRowLengthSupport = false;
        fPackFlipYSupport =
            ctxInfo.hasExtension("GL_ANGLE_pack_reverse_row_order");
    }

    fTextureUsageSupport = (kES2_GrGLBinding == binding) &&
                            ctxInfo.hasExtension("GL_ANGLE_texture_usage");

    // Tex storage is in desktop 4.2 and can be an extension to desktop or ES.
    fTexStorageSupport = (kDesktop_GrGLBinding == binding &&
                          version >= GR_GL_VER(4,2)) ||
                         ctxInfo.hasExtension("GL_ARB_texture_storage") ||
                         ctxInfo.hasExtension("GL_EXT_texture_storage");

    // ARB_texture_rg is part of OpenGL 3.0
    if (kDesktop_GrGLBinding == binding) {
        fTextureRedSupport = version >= GR_GL_VER(3,0) ||
                             ctxInfo.hasExtension("GL_ARB_texture_rg");
    } else {
        fTextureRedSupport = ctxInfo.hasExtension("GL_EXT_texture_rg");
    }

    fImagingSupport = kDesktop_GrGLBinding == binding &&
                      ctxInfo.hasExtension("GL_ARB_imaging");

    // ES 2 only guarantees RGBA/uchar + one other format/type combo for
    // ReadPixels. The other format has to checked at run-time since it
    // can change based on which render target is bound
    fTwoFormatLimit = kES2_GrGLBinding == binding;

    // Known issue on at least some Intel platforms:
    // http://code.google.com/p/skia/issues/detail?id=946
    if (kIntel_GrGLVendor != ctxInfo.vendor()) {
        fFragCoordsConventionSupport = ctxInfo.glslGeneration() >= k150_GrGLSLGeneration ||
                                       ctxInfo.hasExtension("GL_ARB_fragment_coord_conventions");
    }

    this->initFSAASupport(ctxInfo);
    this->initStencilFormats(ctxInfo);
}

void GrGLCaps::init(const GrGLContextInfo& ctxInfo, const GrGLInterface* gli) {

    this->reset();
    if (!ctxInfo.isInitialized()) {
        return;
    }

    GrGLBinding binding = ctxInfo.binding();
    GrGLVersion version = ctxInfo.version();

    /**************************************************************************
     * Caps specific to GrGLCaps
     **************************************************************************/

    if (kES2_GrGLBinding == binding) {
        GR_GL_GetIntegerv(gli, GR_GL_MAX_FRAGMENT_UNIFORM_VECTORS,
                          &fMaxFragmentUniformVectors);
    } else {
        GrAssert(kDesktop_GrGLBinding == binding);
        GrGLint max;
        GR_GL_GetIntegerv(gli, GR_GL_MAX_FRAGMENT_UNIFORM_COMPONENTS, &max);
        fMaxFragmentUniformVectors = max / 4;
    }
    GR_GL_GetIntegerv(gli, GR_GL_MAX_VERTEX_ATTRIBS, &fMaxVertexAttributes);

    if (kDesktop_GrGLBinding == binding) {
        fRGBA8RenderbufferSupport = true;
    } else {
        fRGBA8RenderbufferSupport = ctxInfo.hasExtension("GL_OES_rgb8_rgba8") ||
                                    ctxInfo.hasExtension("GL_ARM_rgba8");
    }

    if (kDesktop_GrGLBinding == binding) {
        fBGRAFormatSupport = version >= GR_GL_VER(1,2) ||
                             ctxInfo.hasExtension("GL_EXT_bgra");
    } else {
        if (ctxInfo.hasExtension("GL_APPLE_texture_format_BGRA8888")) {
            fBGRAFormatSupport = true;
        } else if (ctxInfo.hasExtension("GL_EXT_texture_format_BGRA8888")) {
            fBGRAFormatSupport = true;
            fBGRAIsInternalFormat = true;
        }
        GrAssert(fBGRAFormatSupport ||
                 kSkia8888_GrPixelConfig != kBGRA_8888_GrPixelConfig);
    }

    if (kDesktop_GrGLBinding == binding) {
        fTextureSwizzleSupport = version >= GR_GL_VER(3,3) ||
                                 ctxInfo.hasExtension("GL_ARB_texture_swizzle");
    } else {
        fTextureSwizzleSupport = false;
    }

    if (kDesktop_GrGLBinding == binding) {
        fUnpackRowLengthSupport = true;
        fUnpackFlipYSupport = false;
        fPackRowLengthSupport = true;
        fPackFlipYSupport = false;
    } else {
        fUnpackRowLengthSupport =ctxInfo.hasExtension("GL_EXT_unpack_subimage");
        fUnpackFlipYSupport = ctxInfo.hasExtension("GL_CHROMIUM_flipy");
        // no extension for pack row length
        fPackRowLengthSupport = false;
        fPackFlipYSupport =
            ctxInfo.hasExtension("GL_ANGLE_pack_reverse_row_order");
    }

    fTextureUsageSupport = (kES2_GrGLBinding == binding) &&
                            ctxInfo.hasExtension("GL_ANGLE_texture_usage");

    // Tex storage is in desktop 4.2 and can be an extension to desktop or ES.
    fTexStorageSupport = (kDesktop_GrGLBinding == binding &&
                          version >= GR_GL_VER(4,2)) ||
                         ctxInfo.hasExtension("GL_ARB_texture_storage") ||
                         ctxInfo.hasExtension("GL_EXT_texture_storage");

    // ARB_texture_rg is part of OpenGL 3.0
    if (kDesktop_GrGLBinding == binding) {
        fTextureRedSupport = version >= GR_GL_VER(3,0) ||
                             ctxInfo.hasExtension("GL_ARB_texture_rg");
    } else {
        fTextureRedSupport = ctxInfo.hasExtension("GL_EXT_texture_rg");
    }

    fImagingSupport = kDesktop_GrGLBinding == binding &&
                      ctxInfo.hasExtension("GL_ARB_imaging");

    // ES 2 only guarantees RGBA/uchar + one other format/type combo for
    // ReadPixels. The other format has to checked at run-time since it
    // can change based on which render target is bound
    fTwoFormatLimit = kES2_GrGLBinding == binding;

    // Known issue on at least some Intel platforms:
    // http://code.google.com/p/skia/issues/detail?id=946
    if (kIntel_GrGLVendor != ctxInfo.vendor()) {
        fFragCoordsConventionSupport = ctxInfo.glslGeneration() >= k150_GrGLSLGeneration ||
                                       ctxInfo.hasExtension("GL_ARB_fragment_coord_conventions");
    }

    // SGX and Mali GPUs that are based on a tiled-deferred architecture that have trouble with
//.........这里部分代码省略.........