text: /*
   * 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 "include/core/SkPixmap.h"
  #include "include/core/SkStrokeRec.h"
  #include "include/core/SkTypes.h"
  #include "include/gpu/GrBackendSemaphore.h"
  #include "include/gpu/GrBackendSurface.h"
  #include "include/gpu/GrTypes.h"
  #include "include/private/SkHalf.h"
  #include "include/private/SkTemplates.h"
  #include "include/private/SkTo.h"
  #include "src/core/SkAutoMalloc.h"
  #include "src/core/SkConvertPixels.h"
  #include "src/core/SkMakeUnique.h"
  #include "src/core/SkMipMap.h"
  #include "src/core/SkTraceEvent.h"
  #include "src/gpu/GrContextPriv.h"
  #include "src/gpu/GrCpuBuffer.h"
  #include "src/gpu/GrDataUtils.h"
  #include "src/gpu/GrFixedClip.h"
  #include "src/gpu/GrGpuResourcePriv.h"
  #include "src/gpu/GrMesh.h"
  #include "src/gpu/GrPipeline.h"
  #include "src/gpu/GrProgramInfo.h"
  #include "src/gpu/GrRenderTargetPriv.h"
  #include "src/gpu/GrShaderCaps.h"
  #include "src/gpu/GrSurfaceProxyPriv.h"
  #include "src/gpu/GrTexturePriv.h"
  #include "src/gpu/gl/GrGLBuffer.h"
  #include "src/gpu/gl/GrGLGpu.h"
  #include "src/gpu/gl/GrGLOpsRenderPass.h"
  #include "src/gpu/gl/GrGLSemaphore.h"
  #include "src/gpu/gl/GrGLStencilAttachment.h"
  #include "src/gpu/gl/GrGLTextureRenderTarget.h"
  #include "src/gpu/gl/builders/GrGLShaderStringBuilder.h"
  #include "src/sksl/SkSLCompiler.h"
  
  #include <cmath>
  
  #define GL_CALL(X) GR_GL_CALL(this->glInterface(), X)
  #define GL_CALL_RET(RET, X) GR_GL_CALL_RET(this->glInterface(), RET, X)
  
  #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
  
  //#define USE_NSIGHT
  
  ///////////////////////////////////////////////////////////////////////////////
  
  static const GrGLenum gXfermodeEquation2Blend[] = {
      // Basic OpenGL blend equations.
      GR_GL_FUNC_ADD,
      GR_GL_FUNC_SUBTRACT,
      GR_GL_FUNC_REVERSE_SUBTRACT,
  
      // GL_KHR_blend_equation_advanced.
      GR_GL_SCREEN,
      GR_GL_OVERLAY,
      GR_GL_DARKEN,
      GR_GL_LIGHTEN,
      GR_GL_COLORDODGE,
      GR_GL_COLORBURN,
      GR_GL_HARDLIGHT,
      GR_GL_SOFTLIGHT,
      GR_GL_DIFFERENCE,
      GR_GL_EXCLUSION,
      GR_GL_MULTIPLY,
      GR_GL_HSL_HUE,
      GR_GL_HSL_SATURATION,
      GR_GL_HSL_COLOR,
      GR_GL_HSL_LUMINOSITY,
  
      // Illegal... needs to map to something.
      GR_GL_FUNC_ADD,
  };
  GR_STATIC_ASSERT(0 == kAdd_GrBlendEquation);
  GR_STATIC_ASSERT(1 == kSubtract_GrBlendEquation);
  GR_STATIC_ASSERT(2 == kReverseSubtract_GrBlendEquation);
  GR_STATIC_ASSERT(3 == kScreen_GrBlendEquation);
  GR_STATIC_ASSERT(4 == kOverlay_GrBlendEquation);
  GR_STATIC_ASSERT(5 == kDarken_GrBlendEquation);
  GR_STATIC_ASSERT(6 == kLighten_GrBlendEquation);
  GR_STATIC_ASSERT(7 == kColorDodge_GrBlendEquation);
  GR_STATIC_ASSERT(8 == kColorBurn_GrBlendEquation);
  GR_STATIC_ASSERT(9 == kHardLight_GrBlendEquation);
  GR_STATIC_ASSERT(10 == kSoftLight_GrBlendEquation);
  GR_STATIC_ASSERT(11 == kDifference_GrBlendEquation);
  GR_STATIC_ASSERT(12 == kExclusion_GrBlendEquation);
  GR_STATIC_ASSERT(13 == kMultiply_GrBlendEquation);
  GR_STATIC_ASSERT(14 == kHSLHue_GrBlendEquation);
  GR_STATIC_ASSERT(15 == kHSLSaturation_GrBlendEquation);
  GR_STATIC_ASSERT(16 == kHSLColor_GrBlendEquation);
  GR_STATIC_ASSERT(17 == kHSLLuminosity_GrBlendEquation);
  GR_STATIC_ASSERT(SK_ARRAY_COUNT(gXfermodeEquation2Blend) == kGrBlendEquationCnt);
  
  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,
  
      // Illegal... needs to map to something.
      GR_GL_ZERO,
  };
  
  bool GrGLGpu::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,
  
          // Illegal.
          false,
      };
      return gCoeffReferencesBlendConst[coeff];
      GR_STATIC_ASSERT(kGrBlendCoeffCnt == SK_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(kGrBlendCoeffCnt == SK_ARRAY_COUNT(gXfermodeCoeff2Blend));
  }
  
  //////////////////////////////////////////////////////////////////////////////
  
  static int gl_target_to_binding_index(GrGLenum target) {
      switch (target) {
          case GR_GL_TEXTURE_2D:
              return 0;
          case GR_GL_TEXTURE_RECTANGLE:
              return 1;
          case GR_GL_TEXTURE_EXTERNAL:
              return 2;
      }
      SK_ABORT("Unexpected GL texture target.");
  }
  
  GrGpuResource::UniqueID GrGLGpu::TextureUnitBindings::boundID(GrGLenum target) const {
      return fTargetBindings[gl_target_to_binding_index(target)].fBoundResourceID;
  }
  
  bool GrGLGpu::TextureUnitBindings::hasBeenModified(GrGLenum target) const {
      return fTargetBindings[gl_target_to_binding_index(target)].fHasBeenModified;
  }
  
  void GrGLGpu::TextureUnitBindings::setBoundID(GrGLenum target, GrGpuResource::UniqueID resourceID) {
      int targetIndex = gl_target_to_binding_index(target);
      fTargetBindings[targetIndex].fBoundResourceID = resourceID;
      fTargetBindings[targetIndex].fHasBeenModified = true;
  }
  
  void GrGLGpu::TextureUnitBindings::invalidateForScratchUse(GrGLenum target) {
      this->setBoundID(target, GrGpuResource::UniqueID());
  }
  
  void GrGLGpu::TextureUnitBindings::invalidateAllTargets(bool markUnmodified) {
      for (auto& targetBinding : fTargetBindings) {
          targetBinding.fBoundResourceID.makeInvalid();
          if (markUnmodified) {
              targetBinding.fHasBeenModified = false;
          }
      }
  }
  
  //////////////////////////////////////////////////////////////////////////////
  
  static GrGLenum filter_to_gl_mag_filter(GrSamplerState::Filter filter) {
      switch (filter) {
          case GrSamplerState::Filter::kNearest: return GR_GL_NEAREST;
          case GrSamplerState::Filter::kBilerp:  return GR_GL_LINEAR;
          case GrSamplerState::Filter::kMipMap:  return GR_GL_LINEAR;
      }
      SK_ABORT("Unknown filter");
  }
  
  static GrGLenum filter_to_gl_min_filter(GrSamplerState::Filter filter) {
      switch (filter) {
          case GrSamplerState::Filter::kNearest: return GR_GL_NEAREST;
          case GrSamplerState::Filter::kBilerp:  return GR_GL_LINEAR;
          case GrSamplerState::Filter::kMipMap:  return GR_GL_LINEAR_MIPMAP_LINEAR;
      }
      SK_ABORT("Unknown filter");
  }
  
  static inline GrGLenum wrap_mode_to_gl_wrap(GrSamplerState::WrapMode wrapMode,
                                              const GrCaps& caps) {
      switch (wrapMode) {
          case GrSamplerState::WrapMode::kClamp:        return GR_GL_CLAMP_TO_EDGE;
          case GrSamplerState::WrapMode::kRepeat:       return GR_GL_REPEAT;
          case GrSamplerState::WrapMode::kMirrorRepeat: return GR_GL_MIRRORED_REPEAT;
          case GrSamplerState::WrapMode::kClampToBorder:
              // May not be supported but should have been caught earlier
              SkASSERT(caps.clampToBorderSupport());
              return GR_GL_CLAMP_TO_BORDER;
      }
      SK_ABORT("Unknown wrap mode");
  }
  
  ///////////////////////////////////////////////////////////////////////////////
  
  class GrGLGpu::SamplerObjectCache {
  public:
      SamplerObjectCache(GrGLGpu* gpu) : fGpu(gpu) {
          fNumTextureUnits = fGpu->glCaps().shaderCaps()->maxFragmentSamplers();
          fHWBoundSamplers.reset(new GrGLuint[fNumTextureUnits]);
          std::fill_n(fHWBoundSamplers.get(), fNumTextureUnits, 0);
          std::fill_n(fSamplers, kNumSamplers, 0);
      }
  
      ~SamplerObjectCache() {
          if (!fNumTextureUnits) {
              // We've already been abandoned.
              return;
          }
          for (GrGLuint sampler : fSamplers) {
              // The spec states that "zero" values should be silently ignored, however they still
              // trigger GL errors on some NVIDIA platforms.
              if (sampler) {
                  GR_GL_CALL(fGpu->glInterface(), DeleteSamplers(1, &sampler));
              }
          }
      }
  
      void bindSampler(int unitIdx, const GrSamplerState& state) {
          int index = StateToIndex(state);
          if (!fSamplers[index]) {
              GrGLuint s;
              GR_GL_CALL(fGpu->glInterface(), GenSamplers(1, &s));
              if (!s) {
                  return;
              }
              fSamplers[index] = s;
              auto minFilter = filter_to_gl_min_filter(state.filter());
              auto magFilter = filter_to_gl_mag_filter(state.filter());
              auto wrapX = wrap_mode_to_gl_wrap(state.wrapModeX(), fGpu->glCaps());
              auto wrapY = wrap_mode_to_gl_wrap(state.wrapModeY(), fGpu->glCaps());
              GR_GL_CALL(fGpu->glInterface(),
                         SamplerParameteri(s, GR_GL_TEXTURE_MIN_FILTER, minFilter));
              GR_GL_CALL(fGpu->glInterface(),
                         SamplerParameteri(s, GR_GL_TEXTURE_MAG_FILTER, magFilter));
              GR_GL_CALL(fGpu->glInterface(), SamplerParameteri(s, GR_GL_TEXTURE_WRAP_S, wrapX));
              GR_GL_CALL(fGpu->glInterface(), SamplerParameteri(s, GR_GL_TEXTURE_WRAP_T, wrapY));
          }
          if (fHWBoundSamplers[unitIdx] != fSamplers[index]) {
              GR_GL_CALL(fGpu->glInterface(), BindSampler(unitIdx, fSamplers[index]));
              fHWBoundSamplers[unitIdx] = fSamplers[index];
          }
      }
  
      void invalidateBindings() {
          // When we have sampler support we always use samplers. So setting these to zero will cause
          // a rebind on next usage.
          std::fill_n(fHWBoundSamplers.get(), fNumTextureUnits, 0);
      }
  
      void abandon() {
          fHWBoundSamplers.reset();
          fNumTextureUnits = 0;
      }
  
      void release() {
          if (!fNumTextureUnits) {
              // We've already been abandoned.
              return;
          }
          GR_GL_CALL(fGpu->glInterface(), DeleteSamplers(kNumSamplers, fSamplers));
          std::fill_n(fSamplers, kNumSamplers, 0);
          // Deleting a bound sampler implicitly binds sampler 0.
          std::fill_n(fHWBoundSamplers.get(), fNumTextureUnits, 0);
      }
  
  private:
      static int StateToIndex(const GrSamplerState& state) {
          int filter = static_cast<int>(state.filter());
          SkASSERT(filter >= 0 && filter < 3);
          int wrapX = static_cast<int>(state.wrapModeX());
          SkASSERT(wrapX >= 0 && wrapX < 4);
          int wrapY = static_cast<int>(state.wrapModeY());
          SkASSERT(wrapY >= 0 && wrapY < 4);
          int idx = 16 * filter + 4 * wrapX + wrapY;
          SkASSERT(idx < kNumSamplers);
          return idx;
      }
  
      GrGLGpu* fGpu;
      static constexpr int kNumSamplers = 48;
      std::unique_ptr<GrGLuint[]> fHWBoundSamplers;
      GrGLuint fSamplers[kNumSamplers];
      int fNumTextureUnits;
  };
  
  ///////////////////////////////////////////////////////////////////////////////
  
  sk_sp<GrGpu> GrGLGpu::Make(sk_sp<const GrGLInterface> interface, const GrContextOptions& options,
                             GrContext* context) {
      if (!interface) {
          interface = GrGLMakeNativeInterface();
          // For clients that have written their own GrGLCreateNativeInterface and haven't yet updated
          // to GrGLMakeNativeInterface.
          if (!interface) {
              interface = sk_ref_sp(GrGLCreateNativeInterface());
          }
          if (!interface) {
              return nullptr;
          }
      }
  #ifdef USE_NSIGHT
      const_cast<GrContextOptions&>(options).fSuppressPathRendering = true;
  #endif
      auto glContext = GrGLContext::Make(std::move(interface), options);
      if (!glContext) {
          return nullptr;
      }
      return sk_sp<GrGpu>(new GrGLGpu(std::move(glContext), context));
  }
  
  GrGLGpu::GrGLGpu(std::unique_ptr<GrGLContext> ctx, GrContext* context)
          : GrGpu(context)
          , fGLContext(std::move(ctx))
          , fProgramCache(new ProgramCache(this))
          , fHWProgramID(0)
          , fTempSrcFBOID(0)
          , fTempDstFBOID(0)
          , fStencilClearFBOID(0) {
      SkASSERT(fGLContext);
      GrGLClearErr(this->glInterface());
      fCaps = sk_ref_sp(fGLContext->caps());
  
      fHWTextureUnitBindings.reset(this->numTextureUnits());
  
      this->hwBufferState(GrGpuBufferType::kVertex)->fGLTarget = GR_GL_ARRAY_BUFFER;
      this->hwBufferState(GrGpuBufferType::kIndex)->fGLTarget = GR_GL_ELEMENT_ARRAY_BUFFER;
      if (GrGLCaps::kChromium_TransferBufferType == this->glCaps().transferBufferType()) {
          this->hwBufferState(GrGpuBufferType::kXferCpuToGpu)->fGLTarget =
                  GR_GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM;
          this->hwBufferState(GrGpuBufferType::kXferGpuToCpu)->fGLTarget =
                  GR_GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM;
      } else {
          this->hwBufferState(GrGpuBufferType::kXferCpuToGpu)->fGLTarget = GR_GL_PIXEL_UNPACK_BUFFER;
          this->hwBufferState(GrGpuBufferType::kXferGpuToCpu)->fGLTarget = GR_GL_PIXEL_PACK_BUFFER;
      }
      for (int i = 0; i < kGrGpuBufferTypeCount; ++i) {
          fHWBufferState[i].invalidate();
      }
      GR_STATIC_ASSERT(4 == SK_ARRAY_COUNT(fHWBufferState));
  
      if (this->glCaps().shaderCaps()->pathRenderingSupport()) {
          fPathRendering.reset(new GrGLPathRendering(this));
      }
  
      if (this->glCaps().samplerObjectSupport()) {
          fSamplerObjectCache.reset(new SamplerObjectCache(this));
      }
  }
  
  GrGLGpu::~GrGLGpu() {
      // Ensure any GrGpuResource objects get deleted first, since they may require a working GrGLGpu
      // to release the resources held by the objects themselves.
      fPathRendering.reset();
      fCopyProgramArrayBuffer.reset();
      fMipmapProgramArrayBuffer.reset();
  
      fHWProgram.reset();
      if (fHWProgramID) {
          // detach the current program so there is no confusion on OpenGL's part
          // that we want it to be deleted
          GL_CALL(UseProgram(0));
      }
  
      if (fTempSrcFBOID) {
          this->deleteFramebuffer(fTempSrcFBOID);
      }
      if (fTempDstFBOID) {
          this->deleteFramebuffer(fTempDstFBOID);
      }
      if (fStencilClearFBOID) {
          this->deleteFramebuffer(fStencilClearFBOID);
      }
  
      for (size_t i = 0; i < SK_ARRAY_COUNT(fCopyPrograms); ++i) {
          if (0 != fCopyPrograms[i].fProgram) {
              GL_CALL(DeleteProgram(fCopyPrograms[i].fProgram));
          }
      }
  
      for (size_t i = 0; i < SK_ARRAY_COUNT(fMipmapPrograms); ++i) {
          if (0 != fMipmapPrograms[i].fProgram) {
              GL_CALL(DeleteProgram(fMipmapPrograms[i].fProgram));
          }
      }
  
      delete fProgramCache;
      fSamplerObjectCache.reset();
  }
  
  void GrGLGpu::disconnect(DisconnectType type) {
      INHERITED::disconnect(type);
      if (DisconnectType::kCleanup == type) {
          if (fHWProgramID) {
              GL_CALL(UseProgram(0));
          }
          if (fTempSrcFBOID) {
              this->deleteFramebuffer(fTempSrcFBOID);
          }
          if (fTempDstFBOID) {
              this->deleteFramebuffer(fTempDstFBOID);
          }
          if (fStencilClearFBOID) {
              this->deleteFramebuffer(fStencilClearFBOID);
          }
          for (size_t i = 0; i < SK_ARRAY_COUNT(fCopyPrograms); ++i) {
              if (fCopyPrograms[i].fProgram) {
                  GL_CALL(DeleteProgram(fCopyPrograms[i].fProgram));
              }
          }
          for (size_t i = 0; i < SK_ARRAY_COUNT(fMipmapPrograms); ++i) {
              if (fMipmapPrograms[i].fProgram) {
                  GL_CALL(DeleteProgram(fMipmapPrograms[i].fProgram));
              }
          }
  
          if (fSamplerObjectCache) {
              fSamplerObjectCache->release();
          }
      } else {
          if (fProgramCache) {
              fProgramCache->abandon();
          }
          if (fSamplerObjectCache) {
              fSamplerObjectCache->abandon();
          }
      }
  
      fHWProgram.reset();
      delete fProgramCache;
      fProgramCache = nullptr;
  
      fHWProgramID = 0;
      fTempSrcFBOID = 0;
      fTempDstFBOID = 0;
      fStencilClearFBOID = 0;
      fCopyProgramArrayBuffer.reset();
      for (size_t i = 0; i < SK_ARRAY_COUNT(fCopyPrograms); ++i) {
          fCopyPrograms[i].fProgram = 0;
      }
      fMipmapProgramArrayBuffer.reset();
      for (size_t i = 0; i < SK_ARRAY_COUNT(fMipmapPrograms); ++i) {
          fMipmapPrograms[i].fProgram = 0;
      }
  
      if (this->glCaps().shaderCaps()->pathRenderingSupport()) {
          this->glPathRendering()->disconnect(type);
      }
  }
  
  ///////////////////////////////////////////////////////////////////////////////
  
  void GrGLGpu::onResetContext(uint32_t resetBits) {
      if (resetBits & kMisc_GrGLBackendState) {
          // we don't use the zb at all
          GL_CALL(Disable(GR_GL_DEPTH_TEST));
          GL_CALL(DepthMask(GR_GL_FALSE));
  
          // We don't use face culling.
          GL_CALL(Disable(GR_GL_CULL_FACE));
          // We do use separate stencil. Our algorithms don't care which face is front vs. back so
          // just set this to the default for self-consistency.
          GL_CALL(FrontFace(GR_GL_CCW));
  
          this->hwBufferState(GrGpuBufferType::kXferCpuToGpu)->invalidate();
          this->hwBufferState(GrGpuBufferType::kXferGpuToCpu)->invalidate();
  
          if (GR_IS_GR_GL(this->glStandard())) {
  #ifndef USE_NSIGHT
              // Desktop-only state that we never change
              if (!this->glCaps().isCoreProfile()) {
                  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_INDEX_LOGIC_OP));
              }
              // The windows NVIDIA driver has GL_ARB_imaging in the extension string when using a
              // core profile. This seems like a bug since the core spec removes any mention of
              // GL_ARB_imaging.
              if (this->glCaps().imagingSupport() && !this->glCaps().isCoreProfile()) {
                  GL_CALL(Disable(GR_GL_COLOR_TABLE));
              }
              GL_CALL(Disable(GR_GL_POLYGON_OFFSET_FILL));
  
              if (this->caps()->wireframeMode()) {
                  GL_CALL(PolygonMode(GR_GL_FRONT_AND_BACK, GR_GL_LINE));
              } else {
                  GL_CALL(PolygonMode(GR_GL_FRONT_AND_BACK, GR_GL_FILL));
              }
  #endif
              // 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));
  
          }
  
          if (GR_IS_GR_GL_ES(this->glStandard()) &&
              this->glCaps().fbFetchRequiresEnablePerSample()) {
              // The arm extension requires specifically enabling MSAA fetching per sample.
              // On some devices this may have a perf hit.  Also multiple render targets are disabled
              GL_CALL(Enable(GR_GL_FETCH_PER_SAMPLE));
          }
          fHWWriteToColor = kUnknown_TriState;
          // we only ever use lines in hairline mode
          GL_CALL(LineWidth(1));
          GL_CALL(Disable(GR_GL_DITHER));
  
          fHWClearColor[0] = fHWClearColor[1] = fHWClearColor[2] = fHWClearColor[3] = SK_FloatNaN;
      }
  
      if (resetBits & kMSAAEnable_GrGLBackendState) {
          fMSAAEnabled = kUnknown_TriState;
  
          if (this->caps()->mixedSamplesSupport()) {
              // The skia blend modes all use premultiplied alpha and therefore expect RGBA coverage
              // modulation. This state has no effect when not rendering to a mixed sampled target.
              GL_CALL(CoverageModulation(GR_GL_RGBA));
          }
      }
  
      fHWActiveTextureUnitIdx = -1; // invalid
      fLastPrimitiveType = static_cast<GrPrimitiveType>(-1);
  
      if (resetBits & kTextureBinding_GrGLBackendState) {
          for (int s = 0; s < this->numTextureUnits(); ++s) {
              fHWTextureUnitBindings[s].invalidateAllTargets(false);
          }
          if (fSamplerObjectCache) {
              fSamplerObjectCache->invalidateBindings();
          }
      }
  
      if (resetBits & kBlend_GrGLBackendState) {
          fHWBlendState.invalidate();
      }
  
      if (resetBits & kView_GrGLBackendState) {
          fHWScissorSettings.invalidate();
          fHWWindowRectsState.invalidate();
          fHWViewport.invalidate();
      }
  
      if (resetBits & kStencil_GrGLBackendState) {
          fHWStencilSettings.invalidate();
          fHWStencilTestEnabled = kUnknown_TriState;
      }
  
      // Vertex
      if (resetBits & kVertex_GrGLBackendState) {
          fHWVertexArrayState.invalidate();
          this->hwBufferState(GrGpuBufferType::kVertex)->invalidate();
          this->hwBufferState(GrGpuBufferType::kIndex)->invalidate();
      }
  
      if (resetBits & kRenderTarget_GrGLBackendState) {
          fHWBoundRenderTargetUniqueID.makeInvalid();
          fHWSRGBFramebuffer = kUnknown_TriState;
      }
  
      if (resetBits & kPathRendering_GrGLBackendState) {
          if (this->caps()->shaderCaps()->pathRenderingSupport()) {
              this->glPathRendering()->resetContext();
          }
      }
  
      // we assume these values
      if (resetBits & kPixelStore_GrGLBackendState) {
          if (this->caps()->writePixelsRowBytesSupport()) {
              GL_CALL(PixelStorei(GR_GL_UNPACK_ROW_LENGTH, 0));
          }
          if (this->glCaps().readPixelsRowBytesSupport()) {
              GL_CALL(PixelStorei(GR_GL_PACK_ROW_LENGTH, 0));
          }
          if (this->glCaps().packFlipYSupport()) {
              GL_CALL(PixelStorei(GR_GL_PACK_REVERSE_ROW_ORDER, GR_GL_FALSE));
          }
      }
  
      if (resetBits & kProgram_GrGLBackendState) {
          fHWProgramID = 0;
          fHWProgram.reset();
      }
      ++fResetTimestampForTextureParameters;
  }
  
  static bool check_backend_texture(const GrBackendTexture& backendTex, const GrColorType colorType,
                                    const GrGLCaps& caps, GrGLTexture::Desc* desc,
                                    bool skipRectTexSupportCheck = false) {
      GrGLTextureInfo info;
      if (!backendTex.getGLTextureInfo(&info) || !info.fID || !info.fFormat) {
          return false;
      }
  
      desc->fSize = {backendTex.width(), backendTex.height()};
      desc->fTarget = info.fTarget;
      desc->fID = info.fID;
      desc->fFormat = GrGLFormatFromGLEnum(info.fFormat);
  
      if (desc->fFormat == GrGLFormat::kUnknown) {
          return false;
      }
      if (GR_GL_TEXTURE_EXTERNAL == desc->fTarget) {
          if (!caps.shaderCaps()->externalTextureSupport()) {
              return false;
          }
      } else if (GR_GL_TEXTURE_RECTANGLE == desc->fTarget) {
          if (!caps.rectangleTextureSupport() && !skipRectTexSupportCheck) {
              return false;
          }
      } else if (GR_GL_TEXTURE_2D != desc->fTarget) {
          return false;
      }
      if (backendTex.isProtected()) {
          // Not supported in GL backend at this time.
          return false;
      }
  
      desc->fConfig = caps.getConfigFromBackendFormat(backendTex.getBackendFormat(), colorType);
      SkASSERT(desc->fConfig != kUnknown_GrPixelConfig);
  
      return true;
  }
  
  sk_sp<GrTexture> GrGLGpu::onWrapBackendTexture(const GrBackendTexture& backendTex,
                                                 GrColorType colorType, GrWrapOwnership ownership,
                                                 GrWrapCacheable cacheable, GrIOType ioType) {
      GrGLTexture::Desc desc;
      if (!check_backend_texture(backendTex, colorType, this->glCaps(), &desc)) {
          return nullptr;
      }
  
      if (kBorrow_GrWrapOwnership == ownership) {
          desc.fOwnership = GrBackendObjectOwnership::kBorrowed;
      } else {
          desc.fOwnership = GrBackendObjectOwnership::kOwned;
      }
  
      GrMipMapsStatus mipMapsStatus = backendTex.hasMipMaps() ? GrMipMapsStatus::kValid
                                                              : GrMipMapsStatus::kNotAllocated;
  
      auto texture = GrGLTexture::MakeWrapped(this, mipMapsStatus, desc,
                                              backendTex.getGLTextureParams(), cacheable, ioType);
      // We don't know what parameters are already set on wrapped textures.
      texture->textureParamsModified();
      return texture;
  }
  
  sk_sp<GrTexture> GrGLGpu::onWrapRenderableBackendTexture(const GrBackendTexture& backendTex,
                                                           int sampleCnt,
                                                           GrColorType colorType,
                                                           GrWrapOwnership ownership,
                                                           GrWrapCacheable cacheable) {
      const GrGLCaps& caps = this->glCaps();
  
      GrGLTexture::Desc desc;
      if (!check_backend_texture(backendTex, colorType, this->glCaps(), &desc)) {
          return nullptr;
      }
      SkASSERT(caps.isFormatRenderable(desc.fFormat, sampleCnt));
      SkASSERT(caps.isFormatTexturable(desc.fFormat));
  
      // We don't support rendering to a EXTERNAL texture.
      if (GR_GL_TEXTURE_EXTERNAL == desc.fTarget) {
          return nullptr;
      }
  
      if (kBorrow_GrWrapOwnership == ownership) {
          desc.fOwnership = GrBackendObjectOwnership::kBorrowed;
      } else {
          desc.fOwnership = GrBackendObjectOwnership::kOwned;
      }
  
  
      sampleCnt = caps.getRenderTargetSampleCount(sampleCnt, desc.fFormat);
      SkASSERT(sampleCnt);
  
      GrGLRenderTarget::IDs rtIDs;
      if (!this->createRenderTargetObjects(desc, sampleCnt, &rtIDs)) {
          return nullptr;
      }
  
      GrMipMapsStatus mipMapsStatus = backendTex.hasMipMaps() ? GrMipMapsStatus::kDirty
                                                              : GrMipMapsStatus::kNotAllocated;
  
      sk_sp<GrGLTextureRenderTarget> texRT(GrGLTextureRenderTarget::MakeWrapped(
              this, sampleCnt, desc, backendTex.getGLTextureParams(), rtIDs, cacheable,
              mipMapsStatus));
      texRT->baseLevelWasBoundToFBO();
      // We don't know what parameters are already set on wrapped textures.
      texRT->textureParamsModified();
      return texRT;
  }
  
  sk_sp<GrRenderTarget> GrGLGpu::onWrapBackendRenderTarget(const GrBackendRenderTarget& backendRT,
                                                           GrColorType grColorType) {
      GrGLFramebufferInfo info;
      if (!backendRT.getGLFramebufferInfo(&info)) {
          return nullptr;
      }
  
      if (backendRT.isProtected()) {
          // Not supported in GL at this time.
          return nullptr;
      }
  
      const auto format = backendRT.getBackendFormat().asGLFormat();
      if (!this->glCaps().isFormatRenderable(format, backendRT.sampleCnt())) {
          return nullptr;
      }
  
      GrGLRenderTarget::IDs rtIDs;
      rtIDs.fRTFBOID = info.fFBOID;
      rtIDs.fMSColorRenderbufferID = 0;
      rtIDs.fTexFBOID = GrGLRenderTarget::kUnresolvableFBOID;
      rtIDs.fRTFBOOwnership = GrBackendObjectOwnership::kBorrowed;
  
      GrPixelConfig config = this->caps()->getConfigFromBackendFormat(backendRT.getBackendFormat(),
                                                                      grColorType);
      SkASSERT(kUnknown_GrPixelConfig != config);
  
      const auto size = SkISize::Make(backendRT.width(), backendRT.height());
      int sampleCount = this->glCaps().getRenderTargetSampleCount(backendRT.sampleCnt(), format);
  
      return GrGLRenderTarget::MakeWrapped(this, size, format, config, sampleCount, rtIDs,
                                           backendRT.stencilBits());
  }
  
  sk_sp<GrRenderTarget> GrGLGpu::onWrapBackendTextureAsRenderTarget(const GrBackendTexture& tex,
                                                                    int sampleCnt,
                                                                    GrColorType colorType) {
      GrGLTexture::Desc desc;
      // We do not check whether texture rectangle is supported by Skia - if the caller provided us
      // with a texture rectangle,we assume the necessary support exists.
      if (!check_backend_texture(tex, colorType, this->glCaps(), &desc, true)) {
          return nullptr;
      }
  
      if (!this->glCaps().isFormatRenderable(desc.fFormat, sampleCnt)) {
          return nullptr;
      }
  
      const int sampleCount = this->glCaps().getRenderTargetSampleCount(sampleCnt, desc.fFormat);
      GrGLRenderTarget::IDs rtIDs;
      if (!this->createRenderTargetObjects(desc, sampleCount, &rtIDs)) {
          return nullptr;
      }
      return GrGLRenderTarget::MakeWrapped(this, desc.fSize, desc.fFormat, desc.fConfig, sampleCount,
                                           rtIDs, 0);
  }
  
  static bool check_write_and_transfer_input(GrGLTexture* glTex) {
      if (!glTex) {
          return false;
      }
  
      // Write or transfer of pixels is not implemented for TEXTURE_EXTERNAL textures
      if (GR_GL_TEXTURE_EXTERNAL == glTex->target()) {
          return false;
      }
  
      return true;
  }
  
  bool GrGLGpu::onWritePixels(GrSurface* surface, int left, int top, int width, int height,
                              GrColorType surfaceColorType, GrColorType srcColorType,
                              const GrMipLevel texels[], int mipLevelCount,
                              bool prepForTexSampling) {
      auto glTex = static_cast<GrGLTexture*>(surface->asTexture());
  
      if (!check_write_and_transfer_input(glTex)) {
          return false;
      }
  
      this->bindTextureToScratchUnit(glTex->target(), glTex->textureID());
  
      SkASSERT(!GrGLFormatIsCompressed(glTex->format()));
      return this->uploadTexData(glTex->format(), surfaceColorType, glTex->width(), glTex->height(),
                                 glTex->target(), left, top, width, height, srcColorType, texels,
                                 mipLevelCount);
  }
  
  bool GrGLGpu::onTransferPixelsTo(GrTexture* texture, int left, int top, int width, int height,
                                   GrColorType textureColorType, GrColorType bufferColorType,
                                   GrGpuBuffer* transferBuffer, size_t offset, size_t rowBytes) {
      GrGLTexture* glTex = static_cast<GrGLTexture*>(texture);
  
      // Can't transfer compressed data
      SkASSERT(!GrGLFormatIsCompressed(glTex->format()));
  
      if (!check_write_and_transfer_input(glTex)) {
          return false;
      }
  
      static_assert(sizeof(int) == sizeof(int32_t), "");
      if (width <= 0 || height <= 0) {
          return false;
      }
  
      this->bindTextureToScratchUnit(glTex->target(), glTex->textureID());
  
      SkASSERT(!transferBuffer->isMapped());
      SkASSERT(!transferBuffer->isCpuBuffer());
      const GrGLBuffer* glBuffer = static_cast<const GrGLBuffer*>(transferBuffer);
      this->bindBuffer(GrGpuBufferType::kXferCpuToGpu, glBuffer);
  
      SkDEBUGCODE(
          SkIRect subRect = SkIRect::MakeXYWH(left, top, width, height);
          SkIRect bounds = SkIRect::MakeWH(texture->width(), texture->height());
          SkASSERT(bounds.contains(subRect));
      )
  
      size_t bpp = GrColorTypeBytesPerPixel(bufferColorType);
      const size_t trimRowBytes = width * bpp;
      const void* pixels = (void*)offset;
      if (width < 0 || height < 0) {
          return false;
      }
  
      bool restoreGLRowLength = false;
      if (trimRowBytes != rowBytes) {
          // we should have checked for this support already
          SkASSERT(this->glCaps().writePixelsRowBytesSupport());
          GL_CALL(PixelStorei(GR_GL_UNPACK_ROW_LENGTH, rowBytes / bpp));
          restoreGLRowLength = true;
      }
  
      GrGLFormat textureFormat = glTex->format();
      // External format and type come from the upload data.
      GrGLenum externalFormat = 0;
      GrGLenum externalType = 0;
      this->glCaps().getTexSubImageExternalFormatAndType(
              textureFormat, textureColorType, bufferColorType, &externalFormat, &externalType);
      if (!externalFormat || !externalType) {
          return false;
      }
  
      GL_CALL(PixelStorei(GR_GL_UNPACK_ALIGNMENT, 1));
      GL_CALL(TexSubImage2D(glTex->target(),
                            0,
                            left, top,
                            width,
                            height,
                            externalFormat, externalType,
                            pixels));
  
      if (restoreGLRowLength) {
          GL_CALL(PixelStorei(GR_GL_UNPACK_ROW_LENGTH, 0));
      }
  
      return true;
  }
  
  bool GrGLGpu::onTransferPixelsFrom(GrSurface* surface, int left, int top, int width, int height,
                                     GrColorType surfaceColorType, GrColorType dstColorType,
                                     GrGpuBuffer* transferBuffer, size_t offset) {
      auto* glBuffer = static_cast<GrGLBuffer*>(transferBuffer);
      this->bindBuffer(GrGpuBufferType::kXferGpuToCpu, glBuffer);
      auto offsetAsPtr = reinterpret_cast<void*>(offset);
      return this->readOrTransferPixelsFrom(surface, left, top, width, height, surfaceColorType,
                                            dstColorType, offsetAsPtr, width);
  }
  
  void GrGLGpu::unbindCpuToGpuXferBuffer() {
      auto* xferBufferState = this->hwBufferState(GrGpuBufferType::kXferCpuToGpu);
      if (!xferBufferState->fBoundBufferUniqueID.isInvalid()) {
          GL_CALL(BindBuffer(xferBufferState->fGLTarget, 0));
          xferBufferState->invalidate();
      }
  }
  
  bool GrGLGpu::uploadTexData(GrGLFormat textureFormat, GrColorType textureColorType, int texWidth,
                              int texHeight, GrGLenum target, int left, int top, int width,
                              int height, GrColorType srcColorType, const GrMipLevel texels[],
                              int mipLevelCount, GrMipMapsStatus* mipMapsStatus) {
      // If we're uploading compressed data then we should be using uploadCompressedTexData
      SkASSERT(!GrGLFormatIsCompressed(textureFormat));
  
      SkASSERT(this->glCaps().isFormatTexturable(textureFormat));
      SkDEBUGCODE(
          SkIRect subRect = SkIRect::MakeXYWH(left, top, width, height);
          SkIRect bounds = SkIRect::MakeWH(texWidth, texHeight);
          SkASSERT(bounds.contains(subRect));
      )
      SkASSERT(1 == mipLevelCount ||
               (0 == left && 0 == top && width == texWidth && height == texHeight));
  
      this->unbindCpuToGpuXferBuffer();
  
      const GrGLInterface* interface = this->glInterface();
      const GrGLCaps& caps = this->glCaps();
  
      size_t bpp = GrColorTypeBytesPerPixel(srcColorType);
  
      if (width == 0 || height == 0) {
          return false;
      }
  
      // External format and type come from the upload data.
      GrGLenum externalFormat;
      GrGLenum externalType;
      this->glCaps().getTexSubImageExternalFormatAndType(
              textureFormat, textureColorType, srcColorType, &externalFormat, &externalType);
      if (!externalFormat || !externalType) {
          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;
  
      if (mipMapsStatus) {
          *mipMapsStatus = (mipLevelCount > 1) ?
                  GrMipMapsStatus::kValid : GrMipMapsStatus::kNotAllocated;
      }
  
      GR_GL_CALL(interface, PixelStorei(GR_GL_UNPACK_ALIGNMENT, 1));
  
      for (int currentMipLevel = 0; currentMipLevel < mipLevelCount; currentMipLevel++) {
          if (!texels[currentMipLevel].fPixels) {
              if (mipMapsStatus) {
                  *mipMapsStatus = GrMipMapsStatus::kDirty;
              }
              continue;
          }
          int twoToTheMipLevel = 1 << currentMipLevel;
          const int currentWidth = SkTMax(1, width / twoToTheMipLevel);
          const int currentHeight = SkTMax(1, height / twoToTheMipLevel);
          const size_t trimRowBytes = currentWidth * bpp;
          const size_t rowBytes = texels[currentMipLevel].fRowBytes;
  
          if (caps.writePixelsRowBytesSupport() && (rowBytes != trimRowBytes || restoreGLRowLength)) {
              GrGLint rowLength = static_cast<GrGLint>(rowBytes / bpp);
              GR_GL_CALL(interface, PixelStorei(GR_GL_UNPACK_ROW_LENGTH, rowLength));
              restoreGLRowLength = true;
          }
  
          GL_CALL(TexSubImage2D(target, currentMipLevel, left, top, currentWidth, currentHeight,
                                externalFormat, externalType, texels[currentMipLevel].fPixels));
      }
      if (restoreGLRowLength) {
          SkASSERT(caps.writePixelsRowBytesSupport());
          GL_CALL(PixelStorei(GR_GL_UNPACK_ROW_LENGTH, 0));
      }
      return true;
  }
  
  bool GrGLGpu::uploadCompressedTexData(GrGLFormat format,
                                        SkImage::CompressionType compressionType,
                                        const SkISize& size,
                                        GrGLenum target,
                                        const void* data) {
      SkASSERT(format != GrGLFormat::kUnknown);
      const GrGLCaps& caps = this->glCaps();
  
      // We only need the internal format for compressed 2D textures.
      GrGLenum internalFormat = caps.getTexImageOrStorageInternalFormat(format);
      if (!internalFormat) {
          return 0;
      }
  
      bool useTexStorage = caps.formatSupportsTexStorage(format);
  
      static constexpr int kMipLevelCount = 1;
  
      // Make sure that the width and height that we pass to OpenGL
      // is a multiple of the block size.
      size_t dataSize = GrCompressedDataSize(compressionType, size.width(), size.height());
  
      if (useTexStorage) {
          // We never resize or change formats of textures.
          GL_ALLOC_CALL(
                  this->glInterface(),
                  TexStorage2D(target, kMipLevelCount, internalFormat, size.width(), size.height()));
          GrGLenum error = CHECK_ALLOC_ERROR(this->glInterface());
          if (error != GR_GL_NO_ERROR) {
              return false;
          }
          GL_CALL(CompressedTexSubImage2D(target,
                                          0,  // level
                                          0,  // left
                                          0,  // top
                                          size.width(),
                                          size.height(),
                                          internalFormat,
                                          SkToInt(dataSize),
                                          data));
      } else {
          GL_ALLOC_CALL(this->glInterface(), CompressedTexImage2D(target,
                                                                  0,  // level
                                                                  internalFormat,
                                                                  size.width(),
                                                                  size.height(),
                                                                  0,  // border
                                                                  SkToInt(dataSize),
                                                                  data));
  
          GrGLenum error = CHECK_ALLOC_ERROR(this->glInterface());
          if (error != GR_GL_NO_ERROR) {
              return false;
          }
      }
      return true;
  }
  
  static bool renderbuffer_storage_msaa(const GrGLContext& ctx,
                                        int sampleCount,
                                        GrGLenum format,
                                        int width, int height) {
      CLEAR_ERROR_BEFORE_ALLOC(ctx.interface());
      SkASSERT(GrGLCaps::kNone_MSFBOType != ctx.caps()->msFBOType());
      switch (ctx.caps()->msFBOType()) {
          case GrGLCaps::kStandard_MSFBOType:
              GL_ALLOC_CALL(ctx.interface(),
                              RenderbufferStorageMultisample(GR_GL_RENDERBUFFER,
                                                              sampleCount,
                                                              format,
                                                              width, height));
              break;
          case GrGLCaps::kES_Apple_MSFBOType:
              GL_ALLOC_CALL(ctx.interface(),
                              RenderbufferStorageMultisampleES2APPLE(GR_GL_RENDERBUFFER,
                                                                      sampleCount,
                                                                      format,
                                                                      width, height));
              break;
          case GrGLCaps::kES_EXT_MsToTexture_MSFBOType:
          case GrGLCaps::kES_IMG_MsToTexture_MSFBOType:
              GL_ALLOC_CALL(ctx.interface(),
                              RenderbufferStorageMultisampleES2EXT(GR_GL_RENDERBUFFER,
                                                                  sampleCount,
                                                                  format,
                                                                  width, height));
              break;
          case GrGLCaps::kNone_MSFBOType:
              SK_ABORT("Shouldn't be here if we don't support multisampled renderbuffers.");
              break;
      }
      return (GR_GL_NO_ERROR == CHECK_ALLOC_ERROR(ctx.interface()));
  }
  
  bool GrGLGpu::createRenderTargetObjects(const GrGLTexture::Desc& desc,
                                          int sampleCount,
                                          GrGLRenderTarget::IDs* rtIDs) {
      rtIDs->fMSColorRenderbufferID = 0;
      rtIDs->fRTFBOID = 0;
      rtIDs->fRTFBOOwnership = GrBackendObjectOwnership::kOwned;
      rtIDs->fTexFBOID = 0;
  
      GrGLenum colorRenderbufferFormat = 0; // suppress warning
  
      if (desc.fFormat == GrGLFormat::kUnknown) {
          goto FAILED;
      }
  
      if (sampleCount > 1 && GrGLCaps::kNone_MSFBOType == this->glCaps().msFBOType()) {
          goto FAILED;
      }
  
      GL_CALL(GenFramebuffers(1, &rtIDs->fTexFBOID));
      if (!rtIDs->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. The exception is the IMG multisample extension. With this
      // extension the texture is multisampled when rendered to and then auto-resolves it when it is
      // rendered from.
      if (sampleCount > 1 && this->glCaps().usesMSAARenderBuffers()) {
          GL_CALL(GenFramebuffers(1, &rtIDs->fRTFBOID));
          GL_CALL(GenRenderbuffers(1, &rtIDs->fMSColorRenderbufferID));
          if (!rtIDs->fRTFBOID || !rtIDs->fMSColorRenderbufferID) {
              goto FAILED;
          }
          colorRenderbufferFormat = this->glCaps().getRenderbufferInternalFormat(desc.fFormat);
      } else {
          rtIDs->fRTFBOID = rtIDs->fTexFBOID;
      }
  
      // below here we may bind the FBO
      fHWBoundRenderTargetUniqueID.makeInvalid();
      if (rtIDs->fRTFBOID != rtIDs->fTexFBOID) {
          SkASSERT(sampleCount > 1);
          GL_CALL(BindRenderbuffer(GR_GL_RENDERBUFFER, rtIDs->fMSColorRenderbufferID));
          if (!renderbuffer_storage_msaa(*fGLContext, sampleCount, colorRenderbufferFormat,
                                         desc.fSize.width(), desc.fSize.height())) {
              goto FAILED;
          }
          this->bindFramebuffer(GR_GL_FRAMEBUFFER, rtIDs->fRTFBOID);
          GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                          GR_GL_COLOR_ATTACHMENT0,
                                          GR_GL_RENDERBUFFER,
                                          rtIDs->fMSColorRenderbufferID));
      }
      this->bindFramebuffer(GR_GL_FRAMEBUFFER, rtIDs->fTexFBOID);
  
      if (this->glCaps().usesImplicitMSAAResolve() && sampleCount > 1) {
          GL_CALL(FramebufferTexture2DMultisample(GR_GL_FRAMEBUFFER,
                                                  GR_GL_COLOR_ATTACHMENT0,
                                                  desc.fTarget,
                                                  desc.fID,
                                                  0,
                                                  sampleCount));
      } else {
          GL_CALL(FramebufferTexture2D(GR_GL_FRAMEBUFFER,
                                       GR_GL_COLOR_ATTACHMENT0,
                                       desc.fTarget,
                                       desc.fID,
                                       0));
      }
  
      return true;
  
  FAILED:
      if (rtIDs->fMSColorRenderbufferID) {
          GL_CALL(DeleteRenderbuffers(1, &rtIDs->fMSColorRenderbufferID));
      }
      if (rtIDs->fRTFBOID != rtIDs->fTexFBOID) {
          this->deleteFramebuffer(rtIDs->fRTFBOID);
      }
      if (rtIDs->fTexFBOID) {
          this->deleteFramebuffer(rtIDs->fTexFBOID);
      }
      return false;
  }
  
  // good to set a break-point here to know when createTexture fails
  static sk_sp<GrTexture> return_null_texture() {
  //    SkDEBUGFAIL("null texture");
      return nullptr;
  }
  
  static GrGLTextureParameters::SamplerOverriddenState set_initial_texture_params(
          const GrGLInterface* interface, GrGLenum target) {
      // 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).
      GrGLTextureParameters::SamplerOverriddenState state;
      state.fMinFilter = GR_GL_NEAREST;
      state.fMagFilter = GR_GL_NEAREST;
      state.fWrapS = GR_GL_CLAMP_TO_EDGE;
      state.fWrapT = GR_GL_CLAMP_TO_EDGE;
      GR_GL_CALL(interface, TexParameteri(target, GR_GL_TEXTURE_MAG_FILTER, state.fMagFilter));
      GR_GL_CALL(interface, TexParameteri(target, GR_GL_TEXTURE_MIN_FILTER, state.fMinFilter));
      GR_GL_CALL(interface, TexParameteri(target, GR_GL_TEXTURE_WRAP_S, state.fWrapS));
      GR_GL_CALL(interface, TexParameteri(target, GR_GL_TEXTURE_WRAP_T, state.fWrapT));
      return state;
  }
  
  sk_sp<GrTexture> GrGLGpu::onCreateTexture(const GrSurfaceDesc& desc,
                                            const GrBackendFormat& format,
                                            GrRenderable renderable,
                                            int renderTargetSampleCnt,
                                            SkBudgeted budgeted,
                                            GrProtected isProtected,
                                            int mipLevelCount,
                                            uint32_t levelClearMask) {
      // We don't support protected textures in GL.
      if (isProtected == GrProtected::kYes) {
          return nullptr;
      }
      SkASSERT(GrGLCaps::kNone_MSFBOType != this->glCaps().msFBOType() || renderTargetSampleCnt == 1);
  
      SkASSERT(mipLevelCount > 0);
      GrMipMapsStatus mipMapsStatus =
              mipLevelCount > 1 ? GrMipMapsStatus::kDirty : GrMipMapsStatus::kNotAllocated;
      GrGLTextureParameters::SamplerOverriddenState initialState;
      GrGLTexture::Desc texDesc;
      texDesc.fSize = {desc.fWidth, desc.fHeight};
      texDesc.fTarget = GR_GL_TEXTURE_2D;
      texDesc.fFormat = format.asGLFormat();
      texDesc.fConfig = desc.fConfig;
      texDesc.fOwnership = GrBackendObjectOwnership::kOwned;
      SkASSERT(texDesc.fFormat != GrGLFormat::kUnknown);
      SkASSERT(!GrGLFormatIsCompressed(texDesc.fFormat));
  
      texDesc.fID = this->createTexture2D({desc.fWidth, desc.fHeight}, texDesc.fFormat, renderable,
                                          &initialState, mipLevelCount);
  
      if (!texDesc.fID) {
          return return_null_texture();
      }
  
      sk_sp<GrGLTexture> tex;
      if (renderable == GrRenderable::kYes) {
          // unbind the texture from the texture unit before binding it to the frame buffer
          GL_CALL(BindTexture(texDesc.fTarget, 0));
          GrGLRenderTarget::IDs rtIDDesc;
  
          if (!this->createRenderTargetObjects(texDesc, renderTargetSampleCnt, &rtIDDesc)) {
              GL_CALL(DeleteTextures(1, &texDesc.fID));
              return return_null_texture();
          }
          tex = sk_make_sp<GrGLTextureRenderTarget>(
                  this, budgeted, renderTargetSampleCnt, texDesc, rtIDDesc, mipMapsStatus);
          tex->baseLevelWasBoundToFBO();
      } else {
          tex = sk_make_sp<GrGLTexture>(this, budgeted, texDesc, mipMapsStatus);
      }
      // The non-sampler params are still at their default values.
      tex->parameters()->set(&initialState, GrGLTextureParameters::NonsamplerState(),
                             fResetTimestampForTextureParameters);
      if (levelClearMask) {
          GrGLenum externalFormat, externalType;
          size_t bpp;
          this->glCaps().getTexSubImageZeroFormatTypeAndBpp(texDesc.fFormat, &externalFormat,
                                                            &externalType, &bpp);
          if (this->glCaps().clearTextureSupport()) {
              for (int i = 0; i < mipLevelCount; ++i) {
                  if (levelClearMask & (1U << i)) {
                      GL_CALL(ClearTexImage(tex->textureID(), i, externalFormat, externalType,
                                            nullptr));
                  }
              }
          } else if (this->glCaps().canFormatBeFBOColorAttachment(format.asGLFormat()) &&
                     !this->glCaps().performColorClearsAsDraws()) {
              this->disableScissor();
              this->disableWindowRectangles();
              this->flushColorWrite(true);
              this->flushClearColor(SK_PMColor4fTRANSPARENT);
              for (int i = 0; i < mipLevelCount; ++i) {
                  if (levelClearMask & (1U << i)) {
                      this->bindSurfaceFBOForPixelOps(tex.get(), i, GR_GL_FRAMEBUFFER,
                                                      kDst_TempFBOTarget);
                      GL_CALL(Clear(GR_GL_COLOR_BUFFER_BIT));
                      this->unbindSurfaceFBOForPixelOps(tex.get(), i, GR_GL_FRAMEBUFFER);
                  }
              }
              fHWBoundRenderTargetUniqueID.makeInvalid();
          } else {
              std::unique_ptr<char[]> zeros;
              GL_CALL(PixelStorei(GR_GL_UNPACK_ALIGNMENT, 1));
              for (int i = 0; i < mipLevelCount; ++i) {
                  if (levelClearMask & (1U << i)) {
                      int levelWidth  = SkTMax(1, texDesc.fSize.width()  >> i);
                      int levelHeight = SkTMax(1, texDesc.fSize.height() >> i);
                      // Levels only get smaller as we proceed. Once we create a zeros use it for all
                      // smaller levels that need clearing.
                      if (!zeros) {
                          size_t size = levelWidth * levelHeight * bpp;
                          zeros.reset(new char[size]());
                      }
                      this->bindTextureToScratchUnit(GR_GL_TEXTURE_2D, tex->textureID());
                      GL_CALL(TexSubImage2D(GR_GL_TEXTURE_2D, i, 0, 0, levelWidth, levelHeight,
                                            externalFormat, externalType, zeros.get()));
                  }
              }
          }
      }
      return tex;
  }
  
  sk_sp<GrTexture> GrGLGpu::onCreateCompressedTexture(int width, int height,
                                                      const GrBackendFormat& format,
                                                      SkImage::CompressionType compression,
                                                      SkBudgeted budgeted, const void* data) {
      GrGLTextureParameters::SamplerOverriddenState initialState;
      GrGLTexture::Desc desc;
      desc.fSize = {width, height};
      desc.fTarget = GR_GL_TEXTURE_2D;
      desc.fConfig = GrCompressionTypePixelConfig(compression);
      desc.fOwnership = GrBackendObjectOwnership::kOwned;
      desc.fFormat = format.asGLFormat();
      desc.fID = this->createCompressedTexture2D(desc.fSize, desc.fFormat, compression, &initialState,
                                                 data);
      if (!desc.fID) {
          return nullptr;
      }
      auto tex = sk_make_sp<GrGLTexture>(this, budgeted, desc, GrMipMapsStatus::kNotAllocated);
      // The non-sampler params are still at their default values.
      tex->parameters()->set(&initialState, GrGLTextureParameters::NonsamplerState(),
                             fResetTimestampForTextureParameters);
      return tex;
  }
  
  namespace {
  
  const GrGLuint kUnknownBitCount = GrGLStencilAttachment::kUnknownBitCount;
  
  void inline get_stencil_rb_sizes(const GrGLInterface* gl,
                                   GrGLStencilAttachment::Format* format) {
  
      // we shouldn't ever know one size and not the other
      SkASSERT((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;
          }
      }
  }
  }
  
  int GrGLGpu::getCompatibleStencilIndex(GrGLFormat format) {
      static const int kSize = 16;
      SkASSERT(this->glCaps().canFormatBeFBOColorAttachment(format));
  
      if (!this->glCaps().hasStencilFormatBeenDeterminedForFormat(format)) {
          // Default to unsupported, set this if we find a stencil format that works.
          int firstWorkingStencilFormatIndex = -1;
  
          GrGLuint colorID =
                  this->createTexture2D({kSize, kSize}, format, GrRenderable::kYes, nullptr, 1);
          if (!colorID) {
              return -1;
          }
          // unbind the texture from the texture unit before binding it to the frame buffer
          GL_CALL(BindTexture(GR_GL_TEXTURE_2D, 0));
  
          // Create Framebuffer
          GrGLuint fb = 0;
          GL_CALL(GenFramebuffers(1, &fb));
          this->bindFramebuffer(GR_GL_FRAMEBUFFER, fb);
          fHWBoundRenderTargetUniqueID.makeInvalid();
          GL_CALL(FramebufferTexture2D(GR_GL_FRAMEBUFFER,
                                       GR_GL_COLOR_ATTACHMENT0,
                                       GR_GL_TEXTURE_2D,
                                       colorID,
                                       0));
          GrGLuint sbRBID = 0;
          GL_CALL(GenRenderbuffers(1, &sbRBID));
  
          // look over formats till I find a compatible one
          int stencilFmtCnt = this->glCaps().stencilFormats().count();
          if (sbRBID) {
              GL_CALL(BindRenderbuffer(GR_GL_RENDERBUFFER, sbRBID));
              for (int i = 0; i < stencilFmtCnt && sbRBID; ++i) {
                  const GrGLCaps::StencilFormat& sFmt = this->glCaps().stencilFormats()[i];
                  CLEAR_ERROR_BEFORE_ALLOC(this->glInterface());
                  GL_ALLOC_CALL(this->glInterface(), RenderbufferStorage(GR_GL_RENDERBUFFER,
                                                                         sFmt.fInternalFormat,
                                                                         kSize, kSize));
                  if (GR_GL_NO_ERROR == CHECK_ALLOC_ERROR(this->glInterface())) {
                      GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                                      GR_GL_STENCIL_ATTACHMENT,
                                                      GR_GL_RENDERBUFFER, sbRBID));
                      if (sFmt.fPacked) {
                          GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                                          GR_GL_DEPTH_ATTACHMENT,
                                                          GR_GL_RENDERBUFFER, sbRBID));
                      } else {
                          GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                                          GR_GL_DEPTH_ATTACHMENT,
                                                          GR_GL_RENDERBUFFER, 0));
                      }
                      GrGLenum status;
                      GL_CALL_RET(status, CheckFramebufferStatus(GR_GL_FRAMEBUFFER));
                      if (status == GR_GL_FRAMEBUFFER_COMPLETE) {
                          firstWorkingStencilFormatIndex = i;
                          break;
                      }
                      GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                                      GR_GL_STENCIL_ATTACHMENT,
                                                      GR_GL_RENDERBUFFER, 0));
                      if (sFmt.fPacked) {
                          GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                                          GR_GL_DEPTH_ATTACHMENT,
                                                          GR_GL_RENDERBUFFER, 0));
                      }
                  }
              }
              GL_CALL(DeleteRenderbuffers(1, &sbRBID));
          }
          GL_CALL(DeleteTextures(1, &colorID));
          this->bindFramebuffer(GR_GL_FRAMEBUFFER, 0);
          this->deleteFramebuffer(fb);
          fGLContext->caps()->setStencilFormatIndexForFormat(format, firstWorkingStencilFormatIndex);
      }
      return this->glCaps().getStencilFormatIndexForFormat(format);
  }
  
  GrGLuint GrGLGpu::createCompressedTexture2D(
          const SkISize& size,
          GrGLFormat format,
          SkImage::CompressionType compression,
          GrGLTextureParameters::SamplerOverriddenState* initialState,
          const void* data) {
      if (format == GrGLFormat::kUnknown) {
          return 0;
      }
      GrGLuint id = 0;
      GL_CALL(GenTextures(1, &id));
      if (!id) {
          return 0;
      }
  
      this->bindTextureToScratchUnit(GR_GL_TEXTURE_2D, id);
  
      *initialState = set_initial_texture_params(this->glInterface(), GR_GL_TEXTURE_2D);
  
      if (!this->uploadCompressedTexData(format, compression, size, GR_GL_TEXTURE_2D, data)) {
          GL_CALL(DeleteTextures(1, &id));
          return 0;
      }
      return id;
  }
  
  GrGLuint GrGLGpu::createTexture2D(const SkISize& size,
                                    GrGLFormat format,
                                    GrRenderable renderable,
                                    GrGLTextureParameters::SamplerOverriddenState* initialState,
                                    int mipLevelCount) {
      SkASSERT(format != GrGLFormat::kUnknown);
      SkASSERT(!GrGLFormatIsCompressed(format));
  
      GrGLuint id = 0;
      GL_CALL(GenTextures(1, &id));
  
      if (!id) {
          return 0;
      }
  
      this->bindTextureToScratchUnit(GR_GL_TEXTURE_2D, id);
  
      if (GrRenderable::kYes == renderable && 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 (initialState) {
          *initialState = set_initial_texture_params(this->glInterface(), GR_GL_TEXTURE_2D);
      } else {
          set_initial_texture_params(this->glInterface(), GR_GL_TEXTURE_2D);
      }
  
      GrGLenum internalFormat = this->glCaps().getTexImageOrStorageInternalFormat(format);
  
      bool success = false;
      if (internalFormat) {
          CLEAR_ERROR_BEFORE_ALLOC(this->glInterface());
          if (this->glCaps().formatSupportsTexStorage(format)) {
              GL_ALLOC_CALL(this->glInterface(),
                            TexStorage2D(GR_GL_TEXTURE_2D, SkTMax(mipLevelCount, 1), internalFormat,
                                         size.width(), size.height()));
              success = (GR_GL_NO_ERROR == CHECK_ALLOC_ERROR(this->glInterface()));
          } else {
              GrGLenum externalFormat, externalType;
              this->glCaps().getTexImageExternalFormatAndType(format, &externalFormat, &externalType);
              GrGLenum error = GR_GL_NO_ERROR;
              if (externalFormat && externalType) {
                  for (int level = 0; level < mipLevelCount && error == GR_GL_NO_ERROR; level++) {
                      const int twoToTheMipLevel = 1 << level;
                      const int currentWidth = SkTMax(1, size.width() / twoToTheMipLevel);
                      const int currentHeight = SkTMax(1, size.height() / twoToTheMipLevel);
                      GL_ALLOC_CALL(
                              this->glInterface(),
                              TexImage2D(GR_GL_TEXTURE_2D, level, internalFormat, currentWidth,
                                         currentHeight, 0, externalFormat, externalType, nullptr));
                      error = CHECK_ALLOC_ERROR(this->glInterface());
                  }
                  success = (GR_GL_NO_ERROR == error);
              }
          }
      }
      if (success) {
          return id;
      }
      GL_CALL(DeleteTextures(1, &id));
      return 0;
  }
  
  GrStencilAttachment* GrGLGpu::createStencilAttachmentForRenderTarget(
          const GrRenderTarget* rt, int width, int height, int numStencilSamples) {
      SkASSERT(width >= rt->width());
      SkASSERT(height >= rt->height());
  
      GrGLStencilAttachment::IDDesc sbDesc;
  
      int sIdx = this->getCompatibleStencilIndex(rt->backendFormat().asGLFormat());
      if (sIdx < 0) {
          return nullptr;
      }
  
      if (!sbDesc.fRenderbufferID) {
          GL_CALL(GenRenderbuffers(1, &sbDesc.fRenderbufferID));
      }
      if (!sbDesc.fRenderbufferID) {
          return nullptr;
      }
      GL_CALL(BindRenderbuffer(GR_GL_RENDERBUFFER, sbDesc.fRenderbufferID));
      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.
      if (numStencilSamples > 1) {
          SkAssertResult(renderbuffer_storage_msaa(*fGLContext,
                                                   numStencilSamples,
                                                   sFmt.fInternalFormat,
                                                   width, height));
      } else {
          GL_ALLOC_CALL(this->glInterface(), RenderbufferStorage(GR_GL_RENDERBUFFER,
                                                                 sFmt.fInternalFormat,
                                                                 width, height));
          SkASSERT(GR_GL_NO_ERROR == CHECK_ALLOC_ERROR(this->glInterface()));
      }
      fStats.incStencilAttachmentCreates();
      // After sized formats we attempt an unsized format and take
      // whatever sizes GL gives us. In that case we query for the size.
      GrGLStencilAttachment::Format format = sFmt;
      get_stencil_rb_sizes(this->glInterface(), &format);
      GrGLStencilAttachment* stencil = new GrGLStencilAttachment(this,
                                                                 sbDesc,
                                                                 width,
                                                                 height,
                                                                 numStencilSamples,
                                                                 format);
      return stencil;
  }
  
  ////////////////////////////////////////////////////////////////////////////////
  
  sk_sp<GrGpuBuffer> GrGLGpu::onCreateBuffer(size_t size, GrGpuBufferType intendedType,
                                             GrAccessPattern accessPattern, const void* data) {
      return GrGLBuffer::Make(this, size, intendedType, accessPattern, data);
  }
  
  void GrGLGpu::flushScissor(const GrScissorState& scissorState, int rtWidth, int rtHeight,
                             GrSurfaceOrigin rtOrigin) {
      if (scissorState.enabled()) {
          auto scissor = GrNativeRect::MakeRelativeTo(rtOrigin, rtHeight, scissorState.rect());
          // if the scissor fully contains the viewport then we fall through and
          // disable the scissor test.
          if (!scissor.contains(rtWidth, rtHeight)) {
              if (fHWScissorSettings.fRect != scissor) {
                  GL_CALL(Scissor(scissor.fX, scissor.fY, scissor.fWidth, scissor.fHeight));
                  fHWScissorSettings.fRect = scissor;
              }
              if (kYes_TriState != fHWScissorSettings.fEnabled) {
                  GL_CALL(Enable(GR_GL_SCISSOR_TEST));
                  fHWScissorSettings.fEnabled = kYes_TriState;
              }
              return;
          }
      }
  
      // See fall through note above
      this->disableScissor();
  }
  
  void GrGLGpu::flushWindowRectangles(const GrWindowRectsState& windowState,
                                      const GrGLRenderTarget* rt, GrSurfaceOrigin origin) {
  #ifndef USE_NSIGHT
      typedef GrWindowRectsState::Mode Mode;
      SkASSERT(!windowState.enabled() || rt->renderFBOID()); // Window rects can't be used on-screen.
      SkASSERT(windowState.numWindows() <= this->caps()->maxWindowRectangles());
  
      if (!this->caps()->maxWindowRectangles() ||
          fHWWindowRectsState.knownEqualTo(origin, rt->width(), rt->height(), windowState)) {
          return;
      }
  
      // This is purely a workaround for a spurious warning generated by gcc. Otherwise the above
      // assert would be sufficient. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=5912
      int numWindows = SkTMin(windowState.numWindows(), int(GrWindowRectangles::kMaxWindows));
      SkASSERT(windowState.numWindows() == numWindows);
  
      GrNativeRect glwindows[GrWindowRectangles::kMaxWindows];
      const SkIRect* skwindows = windowState.windows().data();
      for (int i = 0; i < numWindows; ++i) {
          glwindows[i].setRelativeTo(origin, rt->height(), skwindows[i]);
      }
  
      GrGLenum glmode = (Mode::kExclusive == windowState.mode()) ? GR_GL_EXCLUSIVE : GR_GL_INCLUSIVE;
      GL_CALL(WindowRectangles(glmode, numWindows, glwindows->asInts()));
  
      fHWWindowRectsState.set(origin, rt->width(), rt->height(), windowState);
  #endif
  }
  
  void GrGLGpu::disableWindowRectangles() {
  #ifndef USE_NSIGHT
      if (!this->caps()->maxWindowRectangles() || fHWWindowRectsState.knownDisabled()) {
          return;
      }
      GL_CALL(WindowRectangles(GR_GL_EXCLUSIVE, 0, nullptr));
      fHWWindowRectsState.setDisabled();
  #endif
  }
  
  bool GrGLGpu::flushGLState(GrRenderTarget* renderTarget,
                             const GrProgramInfo& programInfo,
                             GrPrimitiveType primitiveType) {
  
      sk_sp<GrGLProgram> program(fProgramCache->refProgram(this, renderTarget, programInfo,
                                                           primitiveType));
      if (!program) {
          GrCapsDebugf(this->caps(), "Failed to create program!\n");
          return false;
      }
  
      this->flushProgram(std::move(program));
  
      // Swizzle the blend to match what the shader will output.
      this->flushBlendAndColorWrite(programInfo.pipeline().getXferProcessor().getBlendInfo(),
                                    programInfo.pipeline().outputSwizzle());
  
      fHWProgram->updateUniformsAndTextureBindings(renderTarget, programInfo);
  
      GrGLRenderTarget* glRT = static_cast<GrGLRenderTarget*>(renderTarget);
      GrStencilSettings stencil;
      if (programInfo.pipeline().isStencilEnabled()) {
          // TODO: attach stencil and create settings during render target flush.
          SkASSERT(glRT->renderTargetPriv().getStencilAttachment());
          stencil.reset(*programInfo.pipeline().getUserStencil(),
                        programInfo.pipeline().hasStencilClip(),
                        glRT->renderTargetPriv().numStencilBits());
      }
      this->flushStencil(stencil, programInfo.origin());
      if (programInfo.pipeline().isScissorEnabled()) {
          static constexpr SkIRect kBogusScissor{0, 0, 1, 1};
          GrScissorState state(programInfo.fixedDynamicState() ? programInfo.fixedScissor()
                                                               : kBogusScissor);
          this->flushScissor(state, glRT->width(), glRT->height(), programInfo.origin());
      } else {
          this->disableScissor();
      }
      this->flushWindowRectangles(programInfo.pipeline().getWindowRectsState(),
                                  glRT, programInfo.origin());
      this->flushHWAAState(glRT, programInfo.pipeline().isHWAntialiasState());
  
      // This must come after textures are flushed because a texture may need
      // to be msaa-resolved (which will modify bound FBO state).
      this->flushRenderTarget(glRT);
  
      return true;
  }
  
  void GrGLGpu::flushProgram(sk_sp<GrGLProgram> program) {
      if (!program) {
          fHWProgram.reset();
          fHWProgramID = 0;
          return;
      }
      SkASSERT((program == fHWProgram) == (fHWProgramID == program->programID()));
      if (program == fHWProgram) {
          return;
      }
      auto id = program->programID();
      SkASSERT(id);
      GL_CALL(UseProgram(id));
      fHWProgram = std::move(program);
      fHWProgramID = id;
  }
  
  void GrGLGpu::flushProgram(GrGLuint id) {
      SkASSERT(id);
      if (fHWProgramID == id) {
          SkASSERT(!fHWProgram);
          return;
      }
      fHWProgram.reset();
      GL_CALL(UseProgram(id));
      fHWProgramID = id;
  }
  
  void GrGLGpu::setupGeometry(const GrBuffer* indexBuffer,
                              const GrBuffer* vertexBuffer,
                              int baseVertex,
                              const GrBuffer* instanceBuffer,
                              int baseInstance,
                              GrPrimitiveRestart enablePrimitiveRestart) {
      SkASSERT((enablePrimitiveRestart == GrPrimitiveRestart::kNo) || indexBuffer);
  
      GrGLAttribArrayState* attribState;
      if (indexBuffer) {
          SkASSERT(indexBuffer->isCpuBuffer() ||
                   !static_cast<const GrGpuBuffer*>(indexBuffer)->isMapped());
          attribState = fHWVertexArrayState.bindInternalVertexArray(this, indexBuffer);
      } else {
          attribState = fHWVertexArrayState.bindInternalVertexArray(this);
      }
  
      int numAttribs = fHWProgram->numVertexAttributes() + fHWProgram->numInstanceAttributes();
      attribState->enableVertexArrays(this, numAttribs, enablePrimitiveRestart);
  
      if (int vertexStride = fHWProgram->vertexStride()) {
          SkASSERT(vertexBuffer);
          SkASSERT(vertexBuffer->isCpuBuffer() ||
                   !static_cast<const GrGpuBuffer*>(vertexBuffer)->isMapped());
          size_t bufferOffset = baseVertex * static_cast<size_t>(vertexStride);
          for (int i = 0; i < fHWProgram->numVertexAttributes(); ++i) {
              const auto& attrib = fHWProgram->vertexAttribute(i);
              static constexpr int kDivisor = 0;
              attribState->set(this, attrib.fLocation, vertexBuffer, attrib.fCPUType, attrib.fGPUType,
                               vertexStride, bufferOffset + attrib.fOffset, kDivisor);
          }
      }
      if (int instanceStride = fHWProgram->instanceStride()) {
          SkASSERT(instanceBuffer);
          SkASSERT(instanceBuffer->isCpuBuffer() ||
                   !static_cast<const GrGpuBuffer*>(instanceBuffer)->isMapped());
          size_t bufferOffset = baseInstance * static_cast<size_t>(instanceStride);
          int attribIdx = fHWProgram->numVertexAttributes();
          for (int i = 0; i < fHWProgram->numInstanceAttributes(); ++i, ++attribIdx) {
              const auto& attrib = fHWProgram->instanceAttribute(i);
              static constexpr int kDivisor = 1;
              attribState->set(this, attrib.fLocation, instanceBuffer, attrib.fCPUType,
                               attrib.fGPUType, instanceStride, bufferOffset + attrib.fOffset,
                               kDivisor);
          }
      }
  }
  
  GrGLenum GrGLGpu::bindBuffer(GrGpuBufferType type, const GrBuffer* buffer) {
      this->handleDirtyContext();
  
      // Index buffer state is tied to the vertex array.
      if (GrGpuBufferType::kIndex == type) {
          this->bindVertexArray(0);
      }
  
      auto* bufferState = this->hwBufferState(type);
      if (buffer->isCpuBuffer()) {
          if (!bufferState->fBufferZeroKnownBound) {
              GL_CALL(BindBuffer(bufferState->fGLTarget, 0));
              bufferState->fBufferZeroKnownBound = true;
              bufferState->fBoundBufferUniqueID.makeInvalid();
          }
      } else if (static_cast<const GrGpuBuffer*>(buffer)->uniqueID() !=
                 bufferState->fBoundBufferUniqueID) {
          const GrGLBuffer* glBuffer = static_cast<const GrGLBuffer*>(buffer);
          GL_CALL(BindBuffer(bufferState->fGLTarget, glBuffer->bufferID()));
          bufferState->fBufferZeroKnownBound = false;
          bufferState->fBoundBufferUniqueID = glBuffer->uniqueID();
      }
  
      return bufferState->fGLTarget;
  }
  void GrGLGpu::disableScissor() {
      if (kNo_TriState != fHWScissorSettings.fEnabled) {
          GL_CALL(Disable(GR_GL_SCISSOR_TEST));
          fHWScissorSettings.fEnabled = kNo_TriState;
          return;
      }
  }
  
  void GrGLGpu::clear(const GrFixedClip& clip, const SkPMColor4f& color,
                      GrRenderTarget* target, GrSurfaceOrigin origin) {
      // parent class should never let us get here with no RT
      SkASSERT(target);
      SkASSERT(!this->caps()->performColorClearsAsDraws());
      SkASSERT(!clip.scissorEnabled() || !this->caps()->performPartialClearsAsDraws());
  
      this->handleDirtyContext();
  
      GrGLRenderTarget* glRT = static_cast<GrGLRenderTarget*>(target);
  
      if (clip.scissorEnabled()) {
          this->flushRenderTarget(glRT, origin, clip.scissorRect());
      } else {
          this->flushRenderTarget(glRT);
      }
      this->flushScissor(clip.scissorState(), glRT->width(), glRT->height(), origin);
      this->flushWindowRectangles(clip.windowRectsState(), glRT, origin);
      this->flushColorWrite(true);
      this->flushClearColor(color);
      GL_CALL(Clear(GR_GL_COLOR_BUFFER_BIT));
  }
  
  void GrGLGpu::clearStencil(GrRenderTarget* target, int clearValue) {
      SkASSERT(!this->caps()->performStencilClearsAsDraws());
  
      if (!target) {
          return;
      }
  
      // This should only be called internally when we know we have a stencil buffer.
      SkASSERT(target->renderTargetPriv().getStencilAttachment());
  
      GrGLRenderTarget* glRT = static_cast<GrGLRenderTarget*>(target);
      this->flushRenderTargetNoColorWrites(glRT);
  
      this->disableScissor();
      this->disableWindowRectangles();
  
      GL_CALL(StencilMask(0xffffffff));
      GL_CALL(ClearStencil(clearValue));
      GL_CALL(Clear(GR_GL_STENCIL_BUFFER_BIT));
      fHWStencilSettings.invalidate();
  }
  
  static bool use_tiled_rendering(const GrGLCaps& glCaps,
                                  const GrOpsRenderPass::StencilLoadAndStoreInfo& stencilLoadStore) {
      // Only use the tiled rendering extension if we can explicitly clear and discard the stencil.
      // Otherwise it's faster to just not use it.
      return glCaps.tiledRenderingSupport() && GrLoadOp::kClear == stencilLoadStore.fLoadOp &&
             GrStoreOp::kDiscard == stencilLoadStore.fStoreOp;
  }
  
  void GrGLGpu::beginCommandBuffer(GrRenderTarget* rt, const SkIRect& bounds, GrSurfaceOrigin origin,
                                   const GrOpsRenderPass::LoadAndStoreInfo& colorLoadStore,
                                   const GrOpsRenderPass::StencilLoadAndStoreInfo& stencilLoadStore) {
      SkASSERT(!fIsExecutingCommandBuffer_DebugOnly);
  
      this->handleDirtyContext();
  
      auto glRT = static_cast<GrGLRenderTarget*>(rt);
      this->flushRenderTarget(glRT);
      SkDEBUGCODE(fIsExecutingCommandBuffer_DebugOnly = true);
  
      if (use_tiled_rendering(this->glCaps(), stencilLoadStore)) {
          auto nativeBounds = GrNativeRect::MakeRelativeTo(origin, glRT->height(), bounds);
          GrGLbitfield preserveMask = (GrLoadOp::kLoad == colorLoadStore.fLoadOp)
                  ? GR_GL_COLOR_BUFFER_BIT0 : GR_GL_NONE;
          SkASSERT(GrLoadOp::kLoad != stencilLoadStore.fLoadOp);  // Handled by use_tiled_rendering().
          GL_CALL(StartTiling(nativeBounds.fX, nativeBounds.fY, nativeBounds.fWidth,
                              nativeBounds.fHeight, preserveMask));
      }
  
      GrGLbitfield clearMask = 0;
      if (GrLoadOp::kClear == colorLoadStore.fLoadOp) {
          SkASSERT(!this->caps()->performColorClearsAsDraws());
          this->flushClearColor(colorLoadStore.fClearColor);
          this->flushColorWrite(true);
          clearMask |= GR_GL_COLOR_BUFFER_BIT;
      }
      if (GrLoadOp::kClear == stencilLoadStore.fLoadOp) {
          SkASSERT(!this->caps()->performStencilClearsAsDraws());
          GL_CALL(StencilMask(0xffffffff));
          GL_CALL(ClearStencil(0));
          clearMask |= GR_GL_STENCIL_BUFFER_BIT;
      }
      if (clearMask) {
          this->disableScissor();
          this->disableWindowRectangles();
          GL_CALL(Clear(clearMask));
      }
  }
  
  void GrGLGpu::endCommandBuffer(GrRenderTarget* rt,
                                 const GrOpsRenderPass::LoadAndStoreInfo& colorLoadStore,
                                 const GrOpsRenderPass::StencilLoadAndStoreInfo& stencilLoadStore) {
      SkASSERT(fIsExecutingCommandBuffer_DebugOnly);
  
      this->handleDirtyContext();
  
      if (rt->uniqueID() != fHWBoundRenderTargetUniqueID) {
          // The framebuffer binding changed in the middle of a command buffer. We should have already
          // printed a warning during onFBOChanged.
          return;
      }
  
      if (GrGLCaps::kNone_InvalidateFBType != this->glCaps().invalidateFBType()) {
          auto glRT = static_cast<GrGLRenderTarget*>(rt);
  
          SkSTArray<2, GrGLenum> discardAttachments;
          if (GrStoreOp::kDiscard == colorLoadStore.fStoreOp) {
              discardAttachments.push_back(
                      (0 == glRT->renderFBOID()) ? GR_GL_COLOR : GR_GL_COLOR_ATTACHMENT0);
          }
          if (GrStoreOp::kDiscard == stencilLoadStore.fStoreOp) {
              discardAttachments.push_back(
                      (0 == glRT->renderFBOID()) ? GR_GL_STENCIL : GR_GL_STENCIL_ATTACHMENT);
          }
  
          if (!discardAttachments.empty()) {
              if (GrGLCaps::kInvalidate_InvalidateFBType == this->glCaps().invalidateFBType()) {
                  GL_CALL(InvalidateFramebuffer(GR_GL_FRAMEBUFFER, discardAttachments.count(),
                                                discardAttachments.begin()));
              } else {
                  SkASSERT(GrGLCaps::kDiscard_InvalidateFBType == this->glCaps().invalidateFBType());
                  GL_CALL(DiscardFramebuffer(GR_GL_FRAMEBUFFER, discardAttachments.count(),
                                             discardAttachments.begin()));
              }
          }
      }
  
      if (use_tiled_rendering(this->glCaps(), stencilLoadStore)) {
          GrGLbitfield preserveMask = (GrStoreOp::kStore == colorLoadStore.fStoreOp)
                  ? GR_GL_COLOR_BUFFER_BIT0 : GR_GL_NONE;
          // Handled by use_tiled_rendering().
          SkASSERT(GrStoreOp::kStore != stencilLoadStore.fStoreOp);
          GL_CALL(EndTiling(preserveMask));
      }
  
      SkDEBUGCODE(fIsExecutingCommandBuffer_DebugOnly = false);
  }
  
  void GrGLGpu::clearStencilClip(const GrFixedClip& clip,
                                 bool insideStencilMask,
                                 GrRenderTarget* target, GrSurfaceOrigin origin) {
      SkASSERT(target);
      SkASSERT(!this->caps()->performStencilClearsAsDraws());
      this->handleDirtyContext();
  
      GrStencilAttachment* sb = target->renderTargetPriv().getStencilAttachment();
      // this should only be called internally when we know we have a
      // stencil buffer.
      SkASSERT(sb);
      GrGLint stencilBitCount =  sb->bits();
  #if 0
      SkASSERT(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 GrOpsTask 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 (insideStencilMask) {
          value = (1 << (stencilBitCount - 1));
      } else {
          value = 0;
      }
      GrGLRenderTarget* glRT = static_cast<GrGLRenderTarget*>(target);
      this->flushRenderTargetNoColorWrites(glRT);
  
      this->flushScissor(clip.scissorState(), glRT->width(), glRT->height(), origin);
      this->flushWindowRectangles(clip.windowRectsState(), glRT, origin);
  
      GL_CALL(StencilMask((uint32_t) clipStencilMask));
      GL_CALL(ClearStencil(value));
      GL_CALL(Clear(GR_GL_STENCIL_BUFFER_BIT));
      fHWStencilSettings.invalidate();
  }
  
  bool GrGLGpu::readOrTransferPixelsFrom(GrSurface* surface, int left, int top, int width, int height,
                                         GrColorType surfaceColorType, GrColorType dstColorType,
                                         void* offsetOrPtr, int rowWidthInPixels) {
      SkASSERT(surface);
  
      auto format = surface->backendFormat().asGLFormat();
      GrGLRenderTarget* renderTarget = static_cast<GrGLRenderTarget*>(surface->asRenderTarget());
      if (!renderTarget && !this->glCaps().isFormatRenderable(format, 1)) {
          return false;
      }
      GrGLenum externalFormat = 0;
      GrGLenum externalType = 0;
      this->glCaps().getReadPixelsFormat(surface->backendFormat().asGLFormat(),
                                         surfaceColorType,
                                         dstColorType,
                                         &externalFormat,
                                         &externalType);
      if (!externalFormat || !externalType) {
          return false;
      }
  
      if (renderTarget) {
          if (renderTarget->numSamples() <= 1 ||
              renderTarget->renderFBOID() == renderTarget->textureFBOID()) {  // Also catches FBO 0.
              SkASSERT(!renderTarget->requiresManualMSAAResolve());
              this->flushRenderTargetNoColorWrites(renderTarget);
          } else if (GrGLRenderTarget::kUnresolvableFBOID == renderTarget->textureFBOID()) {
              SkASSERT(!renderTarget->requiresManualMSAAResolve());
              return false;
          } else {
              SkASSERT(renderTarget->requiresManualMSAAResolve());
              // we don't track the state of the READ FBO ID.
              this->bindFramebuffer(GR_GL_READ_FRAMEBUFFER, renderTarget->textureFBOID());
          }
      } else {
          // Use a temporary FBO.
          this->bindSurfaceFBOForPixelOps(surface, 0, GR_GL_FRAMEBUFFER, kSrc_TempFBOTarget);
          fHWBoundRenderTargetUniqueID.makeInvalid();
      }
  
      // the read rect is viewport-relative
      GrNativeRect readRect = {left, top, width, height};
  
      // determine if GL can read using the passed rowBytes or if we need a scratch buffer.
      if (rowWidthInPixels != width) {
          SkASSERT(this->glCaps().readPixelsRowBytesSupport());
          GL_CALL(PixelStorei(GR_GL_PACK_ROW_LENGTH, rowWidthInPixels));
      }
      GL_CALL(PixelStorei(GR_GL_PACK_ALIGNMENT, 1));
  
      bool reattachStencil = false;
      if (this->glCaps().detachStencilFromMSAABuffersBeforeReadPixels() &&
          renderTarget &&
          renderTarget->renderTargetPriv().getStencilAttachment() &&
          renderTarget->numSamples() > 1) {
          // Fix Adreno devices that won't read from MSAA framebuffers with stencil attached
          reattachStencil = true;
          GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER, GR_GL_STENCIL_ATTACHMENT,
                                          GR_GL_RENDERBUFFER, 0));
      }
  
      GL_CALL(ReadPixels(readRect.fX, readRect.fY, readRect.fWidth, readRect.fHeight,
                         externalFormat, externalType, offsetOrPtr));
  
      if (reattachStencil) {
          GrGLStencilAttachment* stencilAttachment = static_cast<GrGLStencilAttachment*>(
                  renderTarget->renderTargetPriv().getStencilAttachment());
          GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER, GR_GL_STENCIL_ATTACHMENT,
                                          GR_GL_RENDERBUFFER, stencilAttachment->renderbufferID()));
      }
  
      if (rowWidthInPixels != width) {
          SkASSERT(this->glCaps().readPixelsRowBytesSupport());
          GL_CALL(PixelStorei(GR_GL_PACK_ROW_LENGTH, 0));
      }
  
      if (!renderTarget) {
          this->unbindSurfaceFBOForPixelOps(surface, 0, GR_GL_FRAMEBUFFER);
      }
      return true;
  }
  
  bool GrGLGpu::onReadPixels(GrSurface* surface, int left, int top, int width, int height,
                             GrColorType surfaceColorType, GrColorType dstColorType, void* buffer,
                             size_t rowBytes) {
      SkASSERT(surface);
  
      size_t bytesPerPixel = GrColorTypeBytesPerPixel(dstColorType);
  
      // GL_PACK_ROW_LENGTH is in terms of pixels not bytes.
      int rowPixelWidth;
  
      if (rowBytes == SkToSizeT(width * bytesPerPixel)) {
          rowPixelWidth = width;
      } else {
          SkASSERT(!(rowBytes % bytesPerPixel));
          rowPixelWidth = rowBytes / bytesPerPixel;
      }
      return this->readOrTransferPixelsFrom(surface, left, top, width, height, surfaceColorType,
                                            dstColorType, buffer, rowPixelWidth);
  }
  
  GrOpsRenderPass* GrGLGpu::getOpsRenderPass(
          GrRenderTarget* rt, GrSurfaceOrigin origin, const SkIRect& bounds,
          const GrOpsRenderPass::LoadAndStoreInfo& colorInfo,
          const GrOpsRenderPass::StencilLoadAndStoreInfo& stencilInfo,
          const SkTArray<GrTextureProxy*, true>& sampledProxies) {
      if (!fCachedOpsRenderPass) {
          fCachedOpsRenderPass.reset(new GrGLOpsRenderPass(this));
      }
  
      fCachedOpsRenderPass->set(rt, bounds, origin, colorInfo, stencilInfo);
      return fCachedOpsRenderPass.get();
  }
  
  void GrGLGpu::flushRenderTarget(GrGLRenderTarget* target, GrSurfaceOrigin origin,
                                  const SkIRect& bounds) {
      this->flushRenderTargetNoColorWrites(target);
      this->didWriteToSurface(target, origin, &bounds);
  }
  
  void GrGLGpu::flushRenderTarget(GrGLRenderTarget* target) {
      this->flushRenderTargetNoColorWrites(target);
      this->didWriteToSurface(target, kTopLeft_GrSurfaceOrigin, nullptr);
  }
  
  void GrGLGpu::flushRenderTargetNoColorWrites(GrGLRenderTarget* target) {
      SkASSERT(target);
      GrGpuResource::UniqueID rtID = target->uniqueID();
      if (fHWBoundRenderTargetUniqueID != rtID) {
          this->bindFramebuffer(GR_GL_FRAMEBUFFER, target->renderFBOID());
  #ifdef SK_DEBUG
          // don't do this check in Chromium -- this is causing
          // lots of repeated command buffer flushes when the compositor is
          // rendering with Ganesh, which is really slow; even too slow for
          // Debug mode.
          if (kChromium_GrGLDriver != this->glContext().driver()) {
              GrGLenum status;
              GL_CALL_RET(status, CheckFramebufferStatus(GR_GL_FRAMEBUFFER));
              if (status != GR_GL_FRAMEBUFFER_COMPLETE) {
                  SkDebugf("GrGLGpu::flushRenderTarget glCheckFramebufferStatus %x\n", status);
              }
          }
  #endif
          fHWBoundRenderTargetUniqueID = rtID;
          this->flushViewport(target->width(), target->height());
      }
  
      if (this->glCaps().srgbWriteControl()) {
          this->flushFramebufferSRGB(this->caps()->isFormatSRGB(target->backendFormat()));
      }
  }
  
  void GrGLGpu::flushFramebufferSRGB(bool enable) {
      if (enable && kYes_TriState != fHWSRGBFramebuffer) {
          GL_CALL(Enable(GR_GL_FRAMEBUFFER_SRGB));
          fHWSRGBFramebuffer = kYes_TriState;
      } else if (!enable && kNo_TriState != fHWSRGBFramebuffer) {
          GL_CALL(Disable(GR_GL_FRAMEBUFFER_SRGB));
          fHWSRGBFramebuffer = kNo_TriState;
      }
  }
  
  void GrGLGpu::flushViewport(int width, int height) {
      GrNativeRect viewport = {0, 0, width, height};
      if (fHWViewport != viewport) {
          GL_CALL(Viewport(viewport.fX, viewport.fY, viewport.fWidth, viewport.fHeight));
          fHWViewport = viewport;
      }
  }
  
  #define SWAP_PER_DRAW 0
  
  #if SWAP_PER_DRAW
      #if defined(SK_BUILD_FOR_MAC)
          #include <AGL/agl.h>
      #elif defined(SK_BUILD_FOR_WIN)
          #include <gl/GL.h>
          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 GrGLGpu::draw(GrRenderTarget* renderTarget,
                     const GrProgramInfo& programInfo,
                     const GrMesh meshes[],
                     int meshCount) {
      this->handleDirtyContext();
  
      SkASSERT(meshCount); // guaranteed by GrOpsRenderPass::draw
  
      GrPrimitiveType primitiveType = meshes[0].primitiveType();
  
  #ifdef SK_DEBUG
      // kPoints should never be intermingled in with the other primitive types
      for (int i = 1; i < meshCount; ++i) {
          if (primitiveType == GrPrimitiveType::kPoints) {
              SkASSERT(meshes[i].primitiveType() == GrPrimitiveType::kPoints);
          } else {
              SkASSERT(meshes[i].primitiveType() != GrPrimitiveType::kPoints);
          }
      }
  #endif
  
      // Passing 'primitiveType' here is a bit misleading. In GL's case it works out, since
      // GL only cares if it is kPoints or not.
      if (!this->flushGLState(renderTarget, programInfo, primitiveType)) {
          return;
      }
  
      bool hasDynamicScissors = programInfo.hasDynamicScissors();
      bool hasDynamicPrimProcTextures = programInfo.hasDynamicPrimProcTextures();
  
      for (int m = 0; m < meshCount; ++m) {
          if (auto barrierType = programInfo.pipeline().xferBarrierType(renderTarget->asTexture(),
                                                                        *this->caps())) {
              this->xferBarrier(renderTarget, barrierType);
          }
  
          if (hasDynamicScissors) {
              GrGLRenderTarget* glRT = static_cast<GrGLRenderTarget*>(renderTarget);
              this->flushScissor(GrScissorState(programInfo.dynamicScissor(m)),
                                 glRT->width(), glRT->height(), programInfo.origin());
          }
          if (hasDynamicPrimProcTextures) {
              auto texProxyArray = programInfo.dynamicPrimProcTextures(m);
              fHWProgram->updatePrimitiveProcessorTextureBindings(programInfo.primProc(),
                                                                  texProxyArray);
          }
          if (this->glCaps().requiresCullFaceEnableDisableWhenDrawingLinesAfterNonLines() &&
              GrIsPrimTypeLines(meshes[m].primitiveType()) &&
              !GrIsPrimTypeLines(fLastPrimitiveType)) {
              GL_CALL(Enable(GR_GL_CULL_FACE));
              GL_CALL(Disable(GR_GL_CULL_FACE));
          }
          meshes[m].sendToGpu(this);
          fLastPrimitiveType = meshes[m].primitiveType();
      }
  
  #if SWAP_PER_DRAW
      glFlush();
      #if defined(SK_BUILD_FOR_MAC)
          aglSwapBuffers(aglGetCurrentContext());
          int set_a_break_pt_here = 9;
          aglSwapBuffers(aglGetCurrentContext());
      #elif defined(SK_BUILD_FOR_WIN)
          SwapBuf();
          int set_a_break_pt_here = 9;
          SwapBuf();
      #endif
  #endif
  }
  
  static GrGLenum gr_primitive_type_to_gl_mode(GrPrimitiveType primitiveType) {
      switch (primitiveType) {
          case GrPrimitiveType::kTriangles:
              return GR_GL_TRIANGLES;
          case GrPrimitiveType::kTriangleStrip:
              return GR_GL_TRIANGLE_STRIP;
          case GrPrimitiveType::kPoints:
              return GR_GL_POINTS;
          case GrPrimitiveType::kLines:
              return GR_GL_LINES;
          case GrPrimitiveType::kLineStrip:
              return GR_GL_LINE_STRIP;
          case GrPrimitiveType::kPath:
              SK_ABORT("non-mesh-based GrPrimitiveType");
              return 0;
      }
      SK_ABORT("invalid GrPrimitiveType");
  }
  
  void GrGLGpu::sendMeshToGpu(GrPrimitiveType primitiveType, const GrBuffer* vertexBuffer,
                              int vertexCount, int baseVertex) {
      const GrGLenum glPrimType = gr_primitive_type_to_gl_mode(primitiveType);
      if (this->glCaps().drawArraysBaseVertexIsBroken()) {
          this->setupGeometry(nullptr, vertexBuffer, baseVertex, nullptr, 0, GrPrimitiveRestart::kNo);
          GL_CALL(DrawArrays(glPrimType, 0, vertexCount));
      } else {
          this->setupGeometry(nullptr, vertexBuffer, 0, nullptr, 0, GrPrimitiveRestart::kNo);
          GL_CALL(DrawArrays(glPrimType, baseVertex, vertexCount));
      }
      fStats.incNumDraws();
  }
  
  static const GrGLvoid* element_ptr(const GrBuffer* indexBuffer, int baseIndex) {
      size_t baseOffset = baseIndex * sizeof(uint16_t);
      if (indexBuffer->isCpuBuffer()) {
          return static_cast<const GrCpuBuffer*>(indexBuffer)->data() + baseOffset;
      } else {
          return reinterpret_cast<const GrGLvoid*>(baseOffset);
      }
  }
  
  void GrGLGpu::sendIndexedMeshToGpu(GrPrimitiveType primitiveType, const GrBuffer* indexBuffer,
                                     int indexCount, int baseIndex, uint16_t minIndexValue,
                                     uint16_t maxIndexValue, const GrBuffer* vertexBuffer,
                                     int baseVertex, GrPrimitiveRestart enablePrimitiveRestart) {
      const GrGLenum glPrimType = gr_primitive_type_to_gl_mode(primitiveType);
      const GrGLvoid* elementPtr = element_ptr(indexBuffer, baseIndex);
  
      this->setupGeometry(indexBuffer, vertexBuffer, baseVertex, nullptr, 0, enablePrimitiveRestart);
  
      if (this->glCaps().drawRangeElementsSupport()) {
          GL_CALL(DrawRangeElements(glPrimType, minIndexValue, maxIndexValue, indexCount,
                                    GR_GL_UNSIGNED_SHORT, elementPtr));
      } else {
          GL_CALL(DrawElements(glPrimType, indexCount, GR_GL_UNSIGNED_SHORT, elementPtr));
      }
      fStats.incNumDraws();
  }
  
  void GrGLGpu::sendInstancedMeshToGpu(GrPrimitiveType primitiveType, const GrBuffer* vertexBuffer,
                                       int vertexCount, int baseVertex,
                                       const GrBuffer* instanceBuffer, int instanceCount,
                                       int baseInstance) {
      GrGLenum glPrimType = gr_primitive_type_to_gl_mode(primitiveType);
      int maxInstances = this->glCaps().maxInstancesPerDrawWithoutCrashing(instanceCount);
      for (int i = 0; i < instanceCount; i += maxInstances) {
          this->setupGeometry(nullptr, vertexBuffer, 0, instanceBuffer, baseInstance + i,
                              GrPrimitiveRestart::kNo);
          GL_CALL(DrawArraysInstanced(glPrimType, baseVertex, vertexCount,
                                      SkTMin(instanceCount - i, maxInstances)));
          fStats.incNumDraws();
      }
  }
  
  void GrGLGpu::sendIndexedInstancedMeshToGpu(GrPrimitiveType primitiveType,
                                              const GrBuffer* indexBuffer, int indexCount,
                                              int baseIndex, const GrBuffer* vertexBuffer,
                                              int baseVertex, const GrBuffer* instanceBuffer,
                                              int instanceCount, int baseInstance,
                                              GrPrimitiveRestart enablePrimitiveRestart) {
      const GrGLenum glPrimType = gr_primitive_type_to_gl_mode(primitiveType);
      const GrGLvoid* elementPtr = element_ptr(indexBuffer, baseIndex);
      int maxInstances = this->glCaps().maxInstancesPerDrawWithoutCrashing(instanceCount);
      for (int i = 0; i < instanceCount; i += maxInstances) {
          this->setupGeometry(indexBuffer, vertexBuffer, baseVertex, instanceBuffer, baseInstance + i,
                              enablePrimitiveRestart);
          GL_CALL(DrawElementsInstanced(glPrimType, indexCount, GR_GL_UNSIGNED_SHORT, elementPtr,
                                        SkTMin(instanceCount - i, maxInstances)));
          fStats.incNumDraws();
      }
  }
  
  void GrGLGpu::onResolveRenderTarget(GrRenderTarget* target, const SkIRect& resolveRect,
                                      GrSurfaceOrigin resolveOrigin, ForExternalIO) {
      // Some extensions automatically resolves the texture when it is read.
      SkASSERT(this->glCaps().usesMSAARenderBuffers());
  
      GrGLRenderTarget* rt = static_cast<GrGLRenderTarget*>(target);
      SkASSERT(rt->textureFBOID() != rt->renderFBOID());
      SkASSERT(rt->textureFBOID() != 0 && rt->renderFBOID() != 0);
      this->bindFramebuffer(GR_GL_READ_FRAMEBUFFER, rt->renderFBOID());
      this->bindFramebuffer(GR_GL_DRAW_FRAMEBUFFER, rt->textureFBOID());
  
      // make sure we go through flushRenderTarget() since we've modified
      // the bound DRAW FBO ID.
      fHWBoundRenderTargetUniqueID.makeInvalid();
      if (GrGLCaps::kES_Apple_MSFBOType == this->glCaps().msFBOType()) {
          // Apple's extension uses the scissor as the blit bounds.
          GrScissorState scissorState;
          scissorState.set(resolveRect);
          this->flushScissor(scissorState, rt->width(), rt->height(), resolveOrigin);
          this->disableWindowRectangles();
          GL_CALL(ResolveMultisampleFramebuffer());
      } else {
          int l, b, r, t;
          if (GrGLCaps::kResolveMustBeFull_BlitFrambufferFlag &
              this->glCaps().blitFramebufferSupportFlags()) {
              l = 0;
              b = 0;
              r = target->width();
              t = target->height();
          } else {
              auto rect = GrNativeRect::MakeRelativeTo(
                      resolveOrigin, rt->height(), resolveRect);
              l = rect.fX;
              b = rect.fY;
              r = rect.fX + rect.fWidth;
              t = rect.fY + rect.fHeight;
          }
  
          // BlitFrameBuffer respects the scissor, so disable it.
          this->disableScissor();
          this->disableWindowRectangles();
          GL_CALL(BlitFramebuffer(l, b, r, t, l, b, r, t, GR_GL_COLOR_BUFFER_BIT, GR_GL_NEAREST));
      }
  }
  
  namespace {
  
  
  GrGLenum gr_to_gl_stencil_op(GrStencilOp op) {
      static const GrGLenum gTable[kGrStencilOpCount] = {
          GR_GL_KEEP,        // kKeep
          GR_GL_ZERO,        // kZero
          GR_GL_REPLACE,     // kReplace
          GR_GL_INVERT,      // kInvert
          GR_GL_INCR_WRAP,   // kIncWrap
          GR_GL_DECR_WRAP,   // kDecWrap
          GR_GL_INCR,        // kIncClamp
          GR_GL_DECR,        // kDecClamp
      };
      GR_STATIC_ASSERT(0 == (int)GrStencilOp::kKeep);
      GR_STATIC_ASSERT(1 == (int)GrStencilOp::kZero);
      GR_STATIC_ASSERT(2 == (int)GrStencilOp::kReplace);
      GR_STATIC_ASSERT(3 == (int)GrStencilOp::kInvert);
      GR_STATIC_ASSERT(4 == (int)GrStencilOp::kIncWrap);
      GR_STATIC_ASSERT(5 == (int)GrStencilOp::kDecWrap);
      GR_STATIC_ASSERT(6 == (int)GrStencilOp::kIncClamp);
      GR_STATIC_ASSERT(7 == (int)GrStencilOp::kDecClamp);
      SkASSERT(op < (GrStencilOp)kGrStencilOpCount);
      return gTable[(int)op];
  }
  
  void set_gl_stencil(const GrGLInterface* gl,
                      const GrStencilSettings::Face& face,
                      GrGLenum glFace) {
      GrGLenum glFunc = GrToGLStencilFunc(face.fTest);
      GrGLenum glFailOp = gr_to_gl_stencil_op(face.fFailOp);
      GrGLenum glPassOp = gr_to_gl_stencil_op(face.fPassOp);
  
      GrGLint ref = face.fRef;
      GrGLint mask = face.fTestMask;
      GrGLint writeMask = face.fWriteMask;
  
      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, GR_GL_KEEP, 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, GR_GL_KEEP, glPassOp));
      }
  }
  }
  
  void GrGLGpu::flushStencil(const GrStencilSettings& stencilSettings, GrSurfaceOrigin origin) {
      if (stencilSettings.isDisabled()) {
          this->disableStencil();
      } else if (fHWStencilSettings != stencilSettings ||
                 (stencilSettings.isTwoSided() && fHWStencilOrigin != origin)) {
          if (kYes_TriState != fHWStencilTestEnabled) {
              GL_CALL(Enable(GR_GL_STENCIL_TEST));
  
              fHWStencilTestEnabled = kYes_TriState;
          }
          if (stencilSettings.isTwoSided()) {
              set_gl_stencil(this->glInterface(), stencilSettings.front(origin), GR_GL_FRONT);
              set_gl_stencil(this->glInterface(), stencilSettings.back(origin), GR_GL_BACK);
          } else {
              set_gl_stencil(
                      this->glInterface(), stencilSettings.frontAndBack(), GR_GL_FRONT_AND_BACK);
          }
          fHWStencilSettings = stencilSettings;
          fHWStencilOrigin = origin;
      }
  }
  
  void GrGLGpu::disableStencil() {
      if (kNo_TriState != fHWStencilTestEnabled) {
          GL_CALL(Disable(GR_GL_STENCIL_TEST));
  
          fHWStencilTestEnabled = kNo_TriState;
          fHWStencilSettings.invalidate();
      }
  }
  
  void GrGLGpu::flushHWAAState(GrRenderTarget* rt, bool useHWAA) {
      // rt is only optional if useHWAA is false.
      SkASSERT(rt || !useHWAA);
  #ifdef SK_DEBUG
      if (useHWAA && rt->numSamples() <= 1) {
          SkASSERT(this->caps()->mixedSamplesSupport());
          SkASSERT(0 != static_cast<GrGLRenderTarget*>(rt)->renderFBOID());
          SkASSERT(rt->renderTargetPriv().getStencilAttachment());
      }
  #endif
  
      if (this->caps()->multisampleDisableSupport()) {
          if (useHWAA) {
              if (kYes_TriState != fMSAAEnabled) {
                  GL_CALL(Enable(GR_GL_MULTISAMPLE));
                  fMSAAEnabled = kYes_TriState;
              }
          } else {
              if (kNo_TriState != fMSAAEnabled) {
                  GL_CALL(Disable(GR_GL_MULTISAMPLE));
                  fMSAAEnabled = kNo_TriState;
              }
          }
      }
  }
  
  void GrGLGpu::flushBlendAndColorWrite(
          const GrXferProcessor::BlendInfo& blendInfo, const GrSwizzle& swizzle) {
      if (this->glCaps().neverDisableColorWrites() && !blendInfo.fWriteColor) {
          // We need to work around a driver bug by using a blend state that preserves the dst color,
          // rather than disabling color writes.
          GrXferProcessor::BlendInfo preserveDstBlend;
          preserveDstBlend.fSrcBlend = kZero_GrBlendCoeff;
          preserveDstBlend.fDstBlend = kOne_GrBlendCoeff;
          this->flushBlendAndColorWrite(preserveDstBlend, swizzle);
          return;
      }
  
      GrBlendEquation equation = blendInfo.fEquation;
      GrBlendCoeff srcCoeff = blendInfo.fSrcBlend;
      GrBlendCoeff dstCoeff = blendInfo.fDstBlend;
  
      // Any optimization to disable blending should have already been applied and
      // tweaked the equation to "add" or "subtract", and the coeffs to (1, 0).
      bool blendOff =
          ((kAdd_GrBlendEquation == equation || kSubtract_GrBlendEquation == equation) &&
          kOne_GrBlendCoeff == srcCoeff && kZero_GrBlendCoeff == dstCoeff) ||
          !blendInfo.fWriteColor;
  
      if (blendOff) {
          if (kNo_TriState != fHWBlendState.fEnabled) {
              GL_CALL(Disable(GR_GL_BLEND));
  
              // Workaround for the ARM KHR_blend_equation_advanced blacklist issue
              // https://code.google.com/p/skia/issues/detail?id=3943
              if (kARM_GrGLVendor == this->ctxInfo().vendor() &&
                  GrBlendEquationIsAdvanced(fHWBlendState.fEquation)) {
                  SkASSERT(this->caps()->advancedBlendEquationSupport());
                  // Set to any basic blending equation.
                  GrBlendEquation blend_equation = kAdd_GrBlendEquation;
                  GL_CALL(BlendEquation(gXfermodeEquation2Blend[blend_equation]));
                  fHWBlendState.fEquation = blend_equation;
              }
  
              fHWBlendState.fEnabled = kNo_TriState;
          }
      } else {
          if (kYes_TriState != fHWBlendState.fEnabled) {
              GL_CALL(Enable(GR_GL_BLEND));
  
              fHWBlendState.fEnabled = kYes_TriState;
          }
  
          if (fHWBlendState.fEquation != equation) {
              GL_CALL(BlendEquation(gXfermodeEquation2Blend[equation]));
              fHWBlendState.fEquation = equation;
          }
  
          if (GrBlendEquationIsAdvanced(equation)) {
              SkASSERT(this->caps()->advancedBlendEquationSupport());
              // Advanced equations have no other blend state.
              return;
          }
  
          if (fHWBlendState.fSrcCoeff != srcCoeff || fHWBlendState.fDstCoeff != dstCoeff) {
              GL_CALL(BlendFunc(gXfermodeCoeff2Blend[srcCoeff],
                                gXfermodeCoeff2Blend[dstCoeff]));
              fHWBlendState.fSrcCoeff = srcCoeff;
              fHWBlendState.fDstCoeff = dstCoeff;
          }
  
          if ((BlendCoeffReferencesConstant(srcCoeff) || BlendCoeffReferencesConstant(dstCoeff))) {
              SkPMColor4f blendConst = swizzle.applyTo(blendInfo.fBlendConstant);
              if (!fHWBlendState.fConstColorValid || fHWBlendState.fConstColor != blendConst) {
                  GL_CALL(BlendColor(blendConst.fR, blendConst.fG, blendConst.fB, blendConst.fA));
                  fHWBlendState.fConstColor = blendConst;
                  fHWBlendState.fConstColorValid = true;
              }
          }
      }
  
      this->flushColorWrite(blendInfo.fWriteColor);
  }
  
  static void get_gl_swizzle_values(const GrSwizzle& swizzle, GrGLenum glValues[4]) {
      for (int i = 0; i < 4; ++i) {
          switch (swizzle[i]) {
              case 'r': glValues[i] = GR_GL_RED;   break;
              case 'g': glValues[i] = GR_GL_GREEN; break;
              case 'b': glValues[i] = GR_GL_BLUE;  break;
              case 'a': glValues[i] = GR_GL_ALPHA; break;
              case '0': glValues[i] = GR_GL_ZERO;  break;
              case '1': glValues[i] = GR_GL_ONE;   break;
              default:  SK_ABORT("Unsupported component");
          }
      }
  }
  
  void GrGLGpu::bindTexture(int unitIdx, GrSamplerState samplerState, const GrSwizzle& swizzle,
                            GrGLTexture* texture) {
      SkASSERT(texture);
  
  #ifdef SK_DEBUG
      if (!this->caps()->npotTextureTileSupport()) {
          if (samplerState.isRepeated()) {
              const int w = texture->width();
              const int h = texture->height();
              SkASSERT(SkIsPow2(w) && SkIsPow2(h));
          }
      }
  #endif
  
      GrGpuResource::UniqueID textureID = texture->uniqueID();
      GrGLenum target = texture->target();
      if (fHWTextureUnitBindings[unitIdx].boundID(target) != textureID) {
          this->setTextureUnit(unitIdx);
          GL_CALL(BindTexture(target, texture->textureID()));
          fHWTextureUnitBindings[unitIdx].setBoundID(target, textureID);
      }
  
      if (samplerState.filter() == GrSamplerState::Filter::kMipMap) {
          if (!this->caps()->mipMapSupport() ||
              texture->texturePriv().mipMapped() == GrMipMapped::kNo) {
              samplerState.setFilterMode(GrSamplerState::Filter::kBilerp);
          }
      }
  
  #ifdef SK_DEBUG
      // We were supposed to ensure MipMaps were up-to-date before getting here.
      if (samplerState.filter() == GrSamplerState::Filter::kMipMap) {
          SkASSERT(!texture->texturePriv().mipMapsAreDirty());
      }
  #endif
  
      auto timestamp = texture->parameters()->resetTimestamp();
      bool setAll = timestamp < fResetTimestampForTextureParameters;
  
      const GrGLTextureParameters::SamplerOverriddenState* samplerStateToRecord = nullptr;
      GrGLTextureParameters::SamplerOverriddenState newSamplerState;
      if (fSamplerObjectCache) {
          fSamplerObjectCache->bindSampler(unitIdx, samplerState);
      } else {
          const GrGLTextureParameters::SamplerOverriddenState& oldSamplerState =
                  texture->parameters()->samplerOverriddenState();
          samplerStateToRecord = &newSamplerState;
  
          newSamplerState.fMinFilter = filter_to_gl_min_filter(samplerState.filter());
          newSamplerState.fMagFilter = filter_to_gl_mag_filter(samplerState.filter());
  
          newSamplerState.fWrapS = wrap_mode_to_gl_wrap(samplerState.wrapModeX(), this->glCaps());
          newSamplerState.fWrapT = wrap_mode_to_gl_wrap(samplerState.wrapModeY(), this->glCaps());
  
          // These are the OpenGL default values.
          newSamplerState.fMinLOD = -1000.f;
          newSamplerState.fMaxLOD = 1000.f;
  
          if (setAll || newSamplerState.fMagFilter != oldSamplerState.fMagFilter) {
              this->setTextureUnit(unitIdx);
              GL_CALL(TexParameteri(target, GR_GL_TEXTURE_MAG_FILTER, newSamplerState.fMagFilter));
          }
          if (setAll || newSamplerState.fMinFilter != oldSamplerState.fMinFilter) {
              this->setTextureUnit(unitIdx);
              GL_CALL(TexParameteri(target, GR_GL_TEXTURE_MIN_FILTER, newSamplerState.fMinFilter));
          }
          if (this->glCaps().mipMapLevelAndLodControlSupport()) {
              if (setAll || newSamplerState.fMinLOD != oldSamplerState.fMinLOD) {
                  this->setTextureUnit(unitIdx);
                  GL_CALL(TexParameterf(target, GR_GL_TEXTURE_MIN_LOD, newSamplerState.fMinLOD));
              }
              if (setAll || newSamplerState.fMaxLOD != oldSamplerState.fMaxLOD) {
                  this->setTextureUnit(unitIdx);
                  GL_CALL(TexParameterf(target, GR_GL_TEXTURE_MAX_LOD, newSamplerState.fMaxLOD));
              }
          }
          if (setAll || newSamplerState.fWrapS != oldSamplerState.fWrapS) {
              this->setTextureUnit(unitIdx);
              GL_CALL(TexParameteri(target, GR_GL_TEXTURE_WRAP_S, newSamplerState.fWrapS));
          }
          if (setAll || newSamplerState.fWrapT != oldSamplerState.fWrapT) {
              this->setTextureUnit(unitIdx);
              GL_CALL(TexParameteri(target, GR_GL_TEXTURE_WRAP_T, newSamplerState.fWrapT));
          }
          if (this->glCaps().clampToBorderSupport()) {
              // Make sure the border color is transparent black (the default)
              if (setAll || oldSamplerState.fBorderColorInvalid) {
                  this->setTextureUnit(unitIdx);
                  static const GrGLfloat kTransparentBlack[4] = {0.f, 0.f, 0.f, 0.f};
                  GL_CALL(TexParameterfv(target, GR_GL_TEXTURE_BORDER_COLOR, kTransparentBlack));
              }
          }
      }
      GrGLTextureParameters::NonsamplerState newNonsamplerState;
      newNonsamplerState.fBaseMipMapLevel = 0;
      newNonsamplerState.fMaxMipMapLevel = texture->texturePriv().maxMipMapLevel();
  
      const GrGLTextureParameters::NonsamplerState& oldNonsamplerState =
              texture->parameters()->nonsamplerState();
      if (!this->caps()->shaderCaps()->textureSwizzleAppliedInShader()) {
          newNonsamplerState.fSwizzleKey = swizzle.asKey();
          if (setAll || swizzle.asKey() != oldNonsamplerState.fSwizzleKey) {
              GrGLenum glValues[4];
              get_gl_swizzle_values(swizzle, glValues);
              this->setTextureUnit(unitIdx);
              if (GR_IS_GR_GL(this->glStandard())) {
                  GR_STATIC_ASSERT(sizeof(glValues[0]) == sizeof(GrGLint));
                  GL_CALL(TexParameteriv(target, GR_GL_TEXTURE_SWIZZLE_RGBA,
                                         reinterpret_cast<const GrGLint*>(glValues)));
              } else if (GR_IS_GR_GL_ES(this->glStandard())) {
                  // ES3 added swizzle support but not GL_TEXTURE_SWIZZLE_RGBA.
                  GL_CALL(TexParameteri(target, GR_GL_TEXTURE_SWIZZLE_R, glValues[0]));
                  GL_CALL(TexParameteri(target, GR_GL_TEXTURE_SWIZZLE_G, glValues[1]));
                  GL_CALL(TexParameteri(target, GR_GL_TEXTURE_SWIZZLE_B, glValues[2]));
                  GL_CALL(TexParameteri(target, GR_GL_TEXTURE_SWIZZLE_A, glValues[3]));
              }
          }
      }
      // These are not supported in ES2 contexts
      if (this->glCaps().mipMapLevelAndLodControlSupport() &&
          (texture->texturePriv().textureType() != GrTextureType::kExternal ||
           !this->glCaps().dontSetBaseOrMaxLevelForExternalTextures())) {
          if (newNonsamplerState.fBaseMipMapLevel != oldNonsamplerState.fBaseMipMapLevel) {
              this->setTextureUnit(unitIdx);
              GL_CALL(TexParameteri(target, GR_GL_TEXTURE_BASE_LEVEL,
                                    newNonsamplerState.fBaseMipMapLevel));
          }
          if (newNonsamplerState.fMaxMipMapLevel != oldNonsamplerState.fMaxMipMapLevel) {
              this->setTextureUnit(unitIdx);
              GL_CALL(TexParameteri(target, GR_GL_TEXTURE_MAX_LEVEL,
                                    newNonsamplerState.fMaxMipMapLevel));
          }
      }
      texture->parameters()->set(samplerStateToRecord, newNonsamplerState,
                                 fResetTimestampForTextureParameters);
  }
  
  void GrGLGpu::onResetTextureBindings() {
      static constexpr GrGLenum kTargets[] = {GR_GL_TEXTURE_2D, GR_GL_TEXTURE_RECTANGLE,
                                              GR_GL_TEXTURE_EXTERNAL};
      for (int i = 0; i < this->numTextureUnits(); ++i) {
          this->setTextureUnit(i);
          for (auto target : kTargets) {
              if (fHWTextureUnitBindings[i].hasBeenModified(target)) {
                  GL_CALL(BindTexture(target, 0));
              }
          }
          fHWTextureUnitBindings[i].invalidateAllTargets(true);
      }
  }
  
  void GrGLGpu::flushColorWrite(bool writeColor) {
      if (!writeColor) {
          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;
          }
      }
  }
  
  void GrGLGpu::flushClearColor(const SkPMColor4f& color) {
      GrGLfloat r = color.fR, g = color.fG, b = color.fB, a = color.fA;
      if (this->glCaps().clearToBoundaryValuesIsBroken() &&
          (1 == r || 0 == r) && (1 == g || 0 == g) && (1 == b || 0 == b) && (1 == a || 0 == a)) {
          static const GrGLfloat safeAlpha1 = nextafter(1.f, 2.f);
          static const GrGLfloat safeAlpha0 = nextafter(0.f, -1.f);
          a = (1 == a) ? safeAlpha1 : safeAlpha0;
      }
      if (r != fHWClearColor[0] || g != fHWClearColor[1] ||
          b != fHWClearColor[2] || a != fHWClearColor[3]) {
          GL_CALL(ClearColor(r, g, b, a));
          fHWClearColor[0] = r;
          fHWClearColor[1] = g;
          fHWClearColor[2] = b;
          fHWClearColor[3] = a;
      }
  }
  
  void GrGLGpu::setTextureUnit(int unit) {
      SkASSERT(unit >= 0 && unit < this->numTextureUnits());
      if (unit != fHWActiveTextureUnitIdx) {
          GL_CALL(ActiveTexture(GR_GL_TEXTURE0 + unit));
          fHWActiveTextureUnitIdx = unit;
      }
  }
  
  void GrGLGpu::bindTextureToScratchUnit(GrGLenum target, GrGLint textureID) {
      // Bind the last texture unit since it is the least likely to be used by GrGLProgram.
      int lastUnitIdx = this->numTextureUnits() - 1;
      if (lastUnitIdx != fHWActiveTextureUnitIdx) {
          GL_CALL(ActiveTexture(GR_GL_TEXTURE0 + lastUnitIdx));
          fHWActiveTextureUnitIdx = lastUnitIdx;
      }
      // Clear out the this field so that if a GrGLProgram does use this unit it will rebind the
      // correct texture.
      fHWTextureUnitBindings[lastUnitIdx].invalidateForScratchUse(target);
      GL_CALL(BindTexture(target, textureID));
  }
  
  // Determines whether glBlitFramebuffer could be used between src and dst by onCopySurface.
  static inline bool can_blit_framebuffer_for_copy_surface(const GrSurface* dst,
                                                           const GrSurface* src,
                                                           const SkIRect& srcRect,
                                                           const SkIPoint& dstPoint,
                                                           const GrGLCaps& caps) {
      int dstSampleCnt = 0;
      int srcSampleCnt = 0;
      if (const GrRenderTarget* rt = dst->asRenderTarget()) {
          dstSampleCnt = rt->numSamples();
      }
      if (const GrRenderTarget* rt = src->asRenderTarget()) {
          srcSampleCnt = rt->numSamples();
      }
      SkASSERT((dstSampleCnt > 0) == SkToBool(dst->asRenderTarget()));
      SkASSERT((srcSampleCnt > 0) == SkToBool(src->asRenderTarget()));
  
      GrGLFormat dstFormat = dst->backendFormat().asGLFormat();
      GrGLFormat srcFormat = src->backendFormat().asGLFormat();
  
      const GrGLTexture* dstTex = static_cast<const GrGLTexture*>(dst->asTexture());
      const GrGLTexture* srcTex = static_cast<const GrGLTexture*>(src->asTexture());
  
      GrTextureType dstTexType;
      GrTextureType* dstTexTypePtr = nullptr;
      GrTextureType srcTexType;
      GrTextureType* srcTexTypePtr = nullptr;
      if (dstTex) {
          dstTexType = dstTex->texturePriv().textureType();
          dstTexTypePtr = &dstTexType;
      }
      if (srcTex) {
          srcTexType = srcTex->texturePriv().textureType();
          srcTexTypePtr = &srcTexType;
      }
  
      return caps.canCopyAsBlit(dstFormat, dstSampleCnt, dstTexTypePtr,
                                srcFormat, srcSampleCnt, srcTexTypePtr,
                                src->getBoundsRect(), true, srcRect, dstPoint);
  }
  
  static bool rt_has_msaa_render_buffer(const GrGLRenderTarget* rt, const GrGLCaps& glCaps) {
      // A RT has a separate MSAA renderbuffer if:
      // 1) It's multisampled
      // 2) We're using an extension with separate MSAA renderbuffers
      // 3) It's not FBO 0, which is special and always auto-resolves
      return rt->numSamples() > 1 && glCaps.usesMSAARenderBuffers() && rt->renderFBOID() != 0;
  }
  
  static inline bool can_copy_texsubimage(const GrSurface* dst, const GrSurface* src,
                                          const GrGLCaps& caps) {
  
      const GrGLRenderTarget* dstRT = static_cast<const GrGLRenderTarget*>(dst->asRenderTarget());
      const GrGLRenderTarget* srcRT = static_cast<const GrGLRenderTarget*>(src->asRenderTarget());
      const GrGLTexture* dstTex = static_cast<const GrGLTexture*>(dst->asTexture());
      const GrGLTexture* srcTex = static_cast<const GrGLTexture*>(src->asTexture());
  
      bool dstHasMSAARenderBuffer = dstRT ? rt_has_msaa_render_buffer(dstRT, caps) : false;
      bool srcHasMSAARenderBuffer = srcRT ? rt_has_msaa_render_buffer(srcRT, caps) : false;
  
      GrGLFormat dstFormat = dst->backendFormat().asGLFormat();
      GrGLFormat srcFormat = src->backendFormat().asGLFormat();
  
      GrTextureType dstTexType;
      GrTextureType* dstTexTypePtr = nullptr;
      GrTextureType srcTexType;
      GrTextureType* srcTexTypePtr = nullptr;
      if (dstTex) {
          dstTexType = dstTex->texturePriv().textureType();
          dstTexTypePtr = &dstTexType;
      }
      if (srcTex) {
          srcTexType = srcTex->texturePriv().textureType();
          srcTexTypePtr = &srcTexType;
      }
  
      return caps.canCopyTexSubImage(dstFormat, dstHasMSAARenderBuffer, dstTexTypePtr,
                                     srcFormat, srcHasMSAARenderBuffer, srcTexTypePtr);
  }
  
  // If a temporary FBO was created, its non-zero ID is returned.
  void GrGLGpu::bindSurfaceFBOForPixelOps(GrSurface* surface, int mipLevel, GrGLenum fboTarget,
                                          TempFBOTarget tempFBOTarget) {
      GrGLRenderTarget* rt = static_cast<GrGLRenderTarget*>(surface->asRenderTarget());
      if (!rt || mipLevel > 0) {
          SkASSERT(surface->asTexture());
          GrGLTexture* texture = static_cast<GrGLTexture*>(surface->asTexture());
          GrGLuint texID = texture->textureID();
          GrGLenum target = texture->target();
          GrGLuint* tempFBOID;
          tempFBOID = kSrc_TempFBOTarget == tempFBOTarget ? &fTempSrcFBOID : &fTempDstFBOID;
  
          if (0 == *tempFBOID) {
              GR_GL_CALL(this->glInterface(), GenFramebuffers(1, tempFBOID));
          }
  
          this->bindFramebuffer(fboTarget, *tempFBOID);
          GR_GL_CALL(
                  this->glInterface(),
                  FramebufferTexture2D(fboTarget, GR_GL_COLOR_ATTACHMENT0, target, texID, mipLevel));
          if (mipLevel == 0) {
              texture->baseLevelWasBoundToFBO();
          }
      } else {
          this->bindFramebuffer(fboTarget, rt->renderFBOID());
      }
  }
  
  void GrGLGpu::unbindSurfaceFBOForPixelOps(GrSurface* surface, int mipLevel, GrGLenum fboTarget) {
      // bindSurfaceFBOForPixelOps temporarily binds textures that are not render targets to
      if (mipLevel > 0 || !surface->asRenderTarget()) {
          SkASSERT(surface->asTexture());
          GrGLenum textureTarget = static_cast<GrGLTexture*>(surface->asTexture())->target();
          GR_GL_CALL(this->glInterface(), FramebufferTexture2D(fboTarget,
                                                               GR_GL_COLOR_ATTACHMENT0,
                                                               textureTarget,
                                                               0,
                                                               0));
      }
  }
  
  void GrGLGpu::onFBOChanged() {
      if (this->caps()->workarounds().flush_on_framebuffer_change ||
          this->caps()->workarounds().restore_scissor_on_fbo_change) {
          GL_CALL(Flush());
      }
  #ifdef SK_DEBUG
      if (fIsExecutingCommandBuffer_DebugOnly) {
          SkDebugf("WARNING: GL FBO binding changed while executing a command buffer. "
                   "This will severely hurt performance.\n");
      }
  #endif
  }
  
  void GrGLGpu::bindFramebuffer(GrGLenum target, GrGLuint fboid) {
      fStats.incRenderTargetBinds();
      GL_CALL(BindFramebuffer(target, fboid));
      if (target == GR_GL_FRAMEBUFFER || target == GR_GL_DRAW_FRAMEBUFFER) {
          fBoundDrawFramebuffer = fboid;
      }
  
      if (this->caps()->workarounds().restore_scissor_on_fbo_change) {
          // The driver forgets the correct scissor when modifying the FBO binding.
          if (!fHWScissorSettings.fRect.isInvalid()) {
              const GrNativeRect& r = fHWScissorSettings.fRect;
              GL_CALL(Scissor(r.fX, r.fY, r.fWidth, r.fHeight));
          }
      }
  
      this->onFBOChanged();
  }
  
  void GrGLGpu::deleteFramebuffer(GrGLuint fboid) {
      if (fboid == fBoundDrawFramebuffer &&
          this->caps()->workarounds().unbind_attachments_on_bound_render_fbo_delete) {
          // This workaround only applies to deleting currently bound framebuffers
          // on Adreno 420.  Because this is a somewhat rare case, instead of
          // tracking all the attachments of every framebuffer instead just always
          // unbind all attachments.
          GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER, GR_GL_COLOR_ATTACHMENT0,
                                          GR_GL_RENDERBUFFER, 0));
          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));
      }
  
      GL_CALL(DeleteFramebuffers(1, &fboid));
  
      // Deleting the currently bound framebuffer rebinds to 0.
      if (fboid == fBoundDrawFramebuffer) {
          this->onFBOChanged();
      }
  }
  
  bool GrGLGpu::onCopySurface(GrSurface* dst, GrSurface* src, const SkIRect& srcRect,
                              const SkIPoint& dstPoint) {
      // Don't prefer copying as a draw if the dst doesn't already have a FBO object.
      // This implicitly handles this->glCaps().useDrawInsteadOfAllRenderTargetWrites().
      bool preferCopy = SkToBool(dst->asRenderTarget());
      auto dstFormat = dst->backendFormat().asGLFormat();
      if (preferCopy && this->glCaps().canCopyAsDraw(dstFormat, SkToBool(src->asTexture()))) {
          if (this->copySurfaceAsDraw(dst, src, srcRect, dstPoint)) {
              return true;
          }
      }
  
      if (can_copy_texsubimage(dst, src, this->glCaps())) {
          this->copySurfaceAsCopyTexSubImage(dst, src, srcRect, dstPoint);
          return true;
      }
  
      if (can_blit_framebuffer_for_copy_surface(dst, src, srcRect, dstPoint, this->glCaps())) {
          return this->copySurfaceAsBlitFramebuffer(dst, src, srcRect, dstPoint);
      }
  
      if (!preferCopy && this->glCaps().canCopyAsDraw(dstFormat, SkToBool(src->asTexture()))) {
          if (this->copySurfaceAsDraw(dst, src, srcRect, dstPoint)) {
              return true;
          }
      }
  
      return false;
  }
  
  bool GrGLGpu::createCopyProgram(GrTexture* srcTex) {
      TRACE_EVENT0("skia.gpu", TRACE_FUNC);
  
      int progIdx = TextureToCopyProgramIdx(srcTex);
      const GrShaderCaps* shaderCaps = this->caps()->shaderCaps();
      GrSLType samplerType =
              GrSLCombinedSamplerTypeForTextureType(srcTex->texturePriv().textureType());
  
      if (!fCopyProgramArrayBuffer) {
          static const GrGLfloat vdata[] = {
              0, 0,
              0, 1,
              1, 0,
              1, 1
          };
          fCopyProgramArrayBuffer = GrGLBuffer::Make(this, sizeof(vdata), GrGpuBufferType::kVertex,
                                                     kStatic_GrAccessPattern, vdata);
      }
      if (!fCopyProgramArrayBuffer) {
          return false;
      }
  
      SkASSERT(!fCopyPrograms[progIdx].fProgram);
      GL_CALL_RET(fCopyPrograms[progIdx].fProgram, CreateProgram());
      if (!fCopyPrograms[progIdx].fProgram) {
          return false;
      }
  
      GrShaderVar aVertex("a_vertex", kHalf2_GrSLType, GrShaderVar::kIn_TypeModifier);
      GrShaderVar uTexCoordXform("u_texCoordXform", kHalf4_GrSLType,
                                 GrShaderVar::kUniform_TypeModifier);
      GrShaderVar uPosXform("u_posXform", kHalf4_GrSLType, GrShaderVar::kUniform_TypeModifier);
      GrShaderVar uTexture("u_texture", samplerType, GrShaderVar::kUniform_TypeModifier);
      GrShaderVar vTexCoord("v_texCoord", kHalf2_GrSLType, GrShaderVar::kOut_TypeModifier);
      GrShaderVar oFragColor("o_FragColor", kHalf4_GrSLType, GrShaderVar::kOut_TypeModifier);
  
      SkString vshaderTxt;
      if (shaderCaps->noperspectiveInterpolationSupport()) {
          if (const char* extension = shaderCaps->noperspectiveInterpolationExtensionString()) {
              vshaderTxt.appendf("#extension %s : require\n", extension);
          }
          vTexCoord.addModifier("noperspective");
      }
  
      aVertex.appendDecl(shaderCaps, &vshaderTxt);
      vshaderTxt.append(";");
      uTexCoordXform.appendDecl(shaderCaps, &vshaderTxt);
      vshaderTxt.append(";");
      uPosXform.appendDecl(shaderCaps, &vshaderTxt);
      vshaderTxt.append(";");
      vTexCoord.appendDecl(shaderCaps, &vshaderTxt);
      vshaderTxt.append(";");
  
      vshaderTxt.append(
          "// Copy Program VS\n"
          "void main() {"
          "  v_texCoord = half2(a_vertex.xy * u_texCoordXform.xy + u_texCoordXform.zw);"
          "  sk_Position.xy = a_vertex * u_posXform.xy + u_posXform.zw;"
          "  sk_Position.zw = half2(0, 1);"
          "}"
      );
  
      SkString fshaderTxt;
      if (shaderCaps->noperspectiveInterpolationSupport()) {
          if (const char* extension = shaderCaps->noperspectiveInterpolationExtensionString()) {
              fshaderTxt.appendf("#extension %s : require\n", extension);
          }
      }
      vTexCoord.setTypeModifier(GrShaderVar::kIn_TypeModifier);
      vTexCoord.appendDecl(shaderCaps, &fshaderTxt);
      fshaderTxt.append(";");
      uTexture.appendDecl(shaderCaps, &fshaderTxt);
      fshaderTxt.append(";");
      fshaderTxt.appendf(
          "// Copy Program FS\n"
          "void main() {"
          "  sk_FragColor = sample(u_texture, v_texCoord);"
          "}"
      );
  
      auto errorHandler = this->getContext()->priv().getShaderErrorHandler();
      SkSL::String sksl(vshaderTxt.c_str(), vshaderTxt.size());
      SkSL::Program::Settings settings;
      settings.fCaps = shaderCaps;
      SkSL::String glsl;
      std::unique_ptr<SkSL::Program> program = GrSkSLtoGLSL(*fGLContext, SkSL::Program::kVertex_Kind,
                                                            sksl, settings, &glsl, errorHandler);
      GrGLuint vshader = GrGLCompileAndAttachShader(*fGLContext, fCopyPrograms[progIdx].fProgram,
                                                    GR_GL_VERTEX_SHADER, glsl, &fStats, errorHandler);
      SkASSERT(program->fInputs.isEmpty());
  
      sksl.assign(fshaderTxt.c_str(), fshaderTxt.size());
      program = GrSkSLtoGLSL(*fGLContext, SkSL::Program::kFragment_Kind, sksl, settings, &glsl,
                             errorHandler);
      GrGLuint fshader = GrGLCompileAndAttachShader(*fGLContext, fCopyPrograms[progIdx].fProgram,
                                                    GR_GL_FRAGMENT_SHADER, glsl, &fStats,
                                                    errorHandler);
      SkASSERT(program->fInputs.isEmpty());
  
      GL_CALL(LinkProgram(fCopyPrograms[progIdx].fProgram));
  
      GL_CALL_RET(fCopyPrograms[progIdx].fTextureUniform,
                  GetUniformLocation(fCopyPrograms[progIdx].fProgram, "u_texture"));
      GL_CALL_RET(fCopyPrograms[progIdx].fPosXformUniform,
                  GetUniformLocation(fCopyPrograms[progIdx].fProgram, "u_posXform"));
      GL_CALL_RET(fCopyPrograms[progIdx].fTexCoordXformUniform,
                  GetUniformLocation(fCopyPrograms[progIdx].fProgram, "u_texCoordXform"));
  
      GL_CALL(BindAttribLocation(fCopyPrograms[progIdx].fProgram, 0, "a_vertex"));
  
      GL_CALL(DeleteShader(vshader));
      GL_CALL(DeleteShader(fshader));
  
      return true;
  }
  
  bool GrGLGpu::createMipmapProgram(int progIdx) {
      const bool oddWidth = SkToBool(progIdx & 0x2);
      const bool oddHeight = SkToBool(progIdx & 0x1);
      const int numTaps = (oddWidth ? 2 : 1) * (oddHeight ? 2 : 1);
  
      const GrShaderCaps* shaderCaps = this->caps()->shaderCaps();
  
      SkASSERT(!fMipmapPrograms[progIdx].fProgram);
      GL_CALL_RET(fMipmapPrograms[progIdx].fProgram, CreateProgram());
      if (!fMipmapPrograms[progIdx].fProgram) {
          return false;
      }
  
      GrShaderVar aVertex("a_vertex", kHalf2_GrSLType, GrShaderVar::kIn_TypeModifier);
      GrShaderVar uTexCoordXform("u_texCoordXform", kHalf4_GrSLType,
                                 GrShaderVar::kUniform_TypeModifier);
      GrShaderVar uTexture("u_texture", kTexture2DSampler_GrSLType,
                           GrShaderVar::kUniform_TypeModifier);
      // We need 1, 2, or 4 texture coordinates (depending on parity of each dimension):
      GrShaderVar vTexCoords[] = {
          GrShaderVar("v_texCoord0", kHalf2_GrSLType, GrShaderVar::kOut_TypeModifier),
          GrShaderVar("v_texCoord1", kHalf2_GrSLType, GrShaderVar::kOut_TypeModifier),
          GrShaderVar("v_texCoord2", kHalf2_GrSLType, GrShaderVar::kOut_TypeModifier),
          GrShaderVar("v_texCoord3", kHalf2_GrSLType, GrShaderVar::kOut_TypeModifier),
      };
      GrShaderVar oFragColor("o_FragColor", kHalf4_GrSLType,GrShaderVar::kOut_TypeModifier);
  
      SkString vshaderTxt;
      if (shaderCaps->noperspectiveInterpolationSupport()) {
          if (const char* extension = shaderCaps->noperspectiveInterpolationExtensionString()) {
              vshaderTxt.appendf("#extension %s : require\n", extension);
          }
          vTexCoords[0].addModifier("noperspective");
          vTexCoords[1].addModifier("noperspective");
          vTexCoords[2].addModifier("noperspective");
          vTexCoords[3].addModifier("noperspective");
      }
  
      aVertex.appendDecl(shaderCaps, &vshaderTxt);
      vshaderTxt.append(";");
      uTexCoordXform.appendDecl(shaderCaps, &vshaderTxt);
      vshaderTxt.append(";");
      for (int i = 0; i < numTaps; ++i) {
          vTexCoords[i].appendDecl(shaderCaps, &vshaderTxt);
          vshaderTxt.append(";");
      }
  
      vshaderTxt.append(
          "// Mipmap Program VS\n"
          "void main() {"
          "  sk_Position.xy = a_vertex * half2(2, 2) - half2(1, 1);"
          "  sk_Position.zw = half2(0, 1);"
      );
  
      // Insert texture coordinate computation:
      if (oddWidth && oddHeight) {
          vshaderTxt.append(
              "  v_texCoord0 = a_vertex.xy * u_texCoordXform.yw;"
              "  v_texCoord1 = a_vertex.xy * u_texCoordXform.yw + half2(u_texCoordXform.x, 0);"
              "  v_texCoord2 = a_vertex.xy * u_texCoordXform.yw + half2(0, u_texCoordXform.z);"
              "  v_texCoord3 = a_vertex.xy * u_texCoordXform.yw + u_texCoordXform.xz;"
          );
      } else if (oddWidth) {
          vshaderTxt.append(
              "  v_texCoord0 = a_vertex.xy * half2(u_texCoordXform.y, 1);"
              "  v_texCoord1 = a_vertex.xy * half2(u_texCoordXform.y, 1) + half2(u_texCoordXform.x, 0);"
          );
      } else if (oddHeight) {
          vshaderTxt.append(
              "  v_texCoord0 = a_vertex.xy * half2(1, u_texCoordXform.w);"
              "  v_texCoord1 = a_vertex.xy * half2(1, u_texCoordXform.w) + half2(0, u_texCoordXform.z);"
          );
      } else {
          vshaderTxt.append(
              "  v_texCoord0 = a_vertex.xy;"
          );
      }
  
      vshaderTxt.append("}");
  
      SkString fshaderTxt;
      if (shaderCaps->noperspectiveInterpolationSupport()) {
          if (const char* extension = shaderCaps->noperspectiveInterpolationExtensionString()) {
              fshaderTxt.appendf("#extension %s : require\n", extension);
          }
      }
      for (int i = 0; i < numTaps; ++i) {
          vTexCoords[i].setTypeModifier(GrShaderVar::kIn_TypeModifier);
          vTexCoords[i].appendDecl(shaderCaps, &fshaderTxt);
          fshaderTxt.append(";");
      }
      uTexture.appendDecl(shaderCaps, &fshaderTxt);
      fshaderTxt.append(";");
      fshaderTxt.append(
          "// Mipmap Program FS\n"
          "void main() {"
      );
  
      if (oddWidth && oddHeight) {
          fshaderTxt.append(
              "  sk_FragColor = (sample(u_texture, v_texCoord0) + "
              "                  sample(u_texture, v_texCoord1) + "
              "                  sample(u_texture, v_texCoord2) + "
              "                  sample(u_texture, v_texCoord3)) * 0.25;"
          );
      } else if (oddWidth || oddHeight) {
          fshaderTxt.append(
              "  sk_FragColor = (sample(u_texture, v_texCoord0) + "
              "                  sample(u_texture, v_texCoord1)) * 0.5;"
          );
      } else {
          fshaderTxt.append(
              "  sk_FragColor = sample(u_texture, v_texCoord0);"
          );
      }
  
      fshaderTxt.append("}");
  
      auto errorHandler = this->getContext()->priv().getShaderErrorHandler();
      SkSL::String sksl(vshaderTxt.c_str(), vshaderTxt.size());
      SkSL::Program::Settings settings;
      settings.fCaps = shaderCaps;
      SkSL::String glsl;
      std::unique_ptr<SkSL::Program> program = GrSkSLtoGLSL(*fGLContext, SkSL::Program::kVertex_Kind,
                                                            sksl, settings, &glsl, errorHandler);
      GrGLuint vshader = GrGLCompileAndAttachShader(*fGLContext, fMipmapPrograms[progIdx].fProgram,
                                                    GR_GL_VERTEX_SHADER, glsl, &fStats, errorHandler);
      SkASSERT(program->fInputs.isEmpty());
  
      sksl.assign(fshaderTxt.c_str(), fshaderTxt.size());
      program = GrSkSLtoGLSL(*fGLContext, SkSL::Program::kFragment_Kind, sksl, settings, &glsl,
                             errorHandler);
      GrGLuint fshader = GrGLCompileAndAttachShader(*fGLContext, fMipmapPrograms[progIdx].fProgram,
                                                    GR_GL_FRAGMENT_SHADER, glsl, &fStats,
                                                    errorHandler);
      SkASSERT(program->fInputs.isEmpty());
  
      GL_CALL(LinkProgram(fMipmapPrograms[progIdx].fProgram));
  
      GL_CALL_RET(fMipmapPrograms[progIdx].fTextureUniform,
                  GetUniformLocation(fMipmapPrograms[progIdx].fProgram, "u_texture"));
      GL_CALL_RET(fMipmapPrograms[progIdx].fTexCoordXformUniform,
                  GetUniformLocation(fMipmapPrograms[progIdx].fProgram, "u_texCoordXform"));
  
      GL_CALL(BindAttribLocation(fMipmapPrograms[progIdx].fProgram, 0, "a_vertex"));
  
      GL_CALL(DeleteShader(vshader));
      GL_CALL(DeleteShader(fshader));
  
      return true;
  }
  
  bool GrGLGpu::copySurfaceAsDraw(GrSurface* dst, GrSurface* src, const SkIRect& srcRect,
                                  const SkIPoint& dstPoint) {
      auto* srcTex = static_cast<GrGLTexture*>(src->asTexture());
      auto* dstTex = static_cast<GrGLTexture*>(src->asTexture());
      auto* dstRT  = static_cast<GrGLRenderTarget*>(src->asRenderTarget());
      if (!srcTex) {
          return false;
      }
      int progIdx = TextureToCopyProgramIdx(srcTex);
      if (!dstRT) {
          SkASSERT(dstTex);
          if (!this->glCaps().isFormatRenderable(dstTex->format(), 1)) {
              return false;
          }
      }
      if (!fCopyPrograms[progIdx].fProgram) {
          if (!this->createCopyProgram(srcTex)) {
              SkDebugf("Failed to create copy program.\n");
              return false;
          }
      }
      int w = srcRect.width();
      int h = srcRect.height();
      // We don't swizzle at all in our copies.
      this->bindTexture(0, GrSamplerState::ClampNearest(), GrSwizzle::RGBA(), srcTex);
      this->bindSurfaceFBOForPixelOps(dst, 0, GR_GL_FRAMEBUFFER, kDst_TempFBOTarget);
      this->flushViewport(dst->width(), dst->height());
      fHWBoundRenderTargetUniqueID.makeInvalid();
      SkIRect dstRect = SkIRect::MakeXYWH(dstPoint.fX, dstPoint.fY, w, h);
      this->flushProgram(fCopyPrograms[progIdx].fProgram);
      fHWVertexArrayState.setVertexArrayID(this, 0);
      GrGLAttribArrayState* attribs = fHWVertexArrayState.bindInternalVertexArray(this);
      attribs->enableVertexArrays(this, 1);
      attribs->set(this, 0, fCopyProgramArrayBuffer.get(), kFloat2_GrVertexAttribType,
                   kFloat2_GrSLType, 2 * sizeof(GrGLfloat), 0);
      // dst rect edges in NDC (-1 to 1)
      int dw = dst->width();
      int dh = dst->height();
      GrGLfloat dx0 = 2.f * dstPoint.fX / dw - 1.f;
      GrGLfloat dx1 = 2.f * (dstPoint.fX + w) / dw - 1.f;
      GrGLfloat dy0 = 2.f * dstPoint.fY / dh - 1.f;
      GrGLfloat dy1 = 2.f * (dstPoint.fY + h) / dh - 1.f;
      GrGLfloat sx0 = (GrGLfloat)srcRect.fLeft;
      GrGLfloat sx1 = (GrGLfloat)(srcRect.fLeft + w);
      GrGLfloat sy0 = (GrGLfloat)srcRect.fTop;
      GrGLfloat sy1 = (GrGLfloat)(srcRect.fTop + h);
      int sw = src->width();
      int sh = src->height();
      if (srcTex->texturePriv().textureType() != GrTextureType::kRectangle) {
          // src rect edges in normalized texture space (0 to 1)
          sx0 /= sw;
          sx1 /= sw;
          sy0 /= sh;
          sy1 /= sh;
      }
      GL_CALL(Uniform4f(fCopyPrograms[progIdx].fPosXformUniform, dx1 - dx0, dy1 - dy0, dx0, dy0));
      GL_CALL(Uniform4f(fCopyPrograms[progIdx].fTexCoordXformUniform,
                        sx1 - sx0, sy1 - sy0, sx0, sy0));
      GL_CALL(Uniform1i(fCopyPrograms[progIdx].fTextureUniform, 0));
      this->flushBlendAndColorWrite(GrXferProcessor::BlendInfo(), GrSwizzle::RGBA());
      this->flushHWAAState(nullptr, false);
      this->disableScissor();
      this->disableWindowRectangles();
      this->disableStencil();
      if (this->glCaps().srgbWriteControl()) {
          this->flushFramebufferSRGB(true);
      }
      GL_CALL(DrawArrays(GR_GL_TRIANGLE_STRIP, 0, 4));
      this->unbindSurfaceFBOForPixelOps(dst, 0, GR_GL_FRAMEBUFFER);
      // The rect is already in device space so we pass in kTopLeft so no flip is done.
      this->didWriteToSurface(dst, kTopLeft_GrSurfaceOrigin, &dstRect);
      return true;
  }
  
  void GrGLGpu::copySurfaceAsCopyTexSubImage(GrSurface* dst, GrSurface* src, const SkIRect& srcRect,
                                             const SkIPoint& dstPoint) {
      SkASSERT(can_copy_texsubimage(dst, src, this->glCaps()));
      this->bindSurfaceFBOForPixelOps(src, 0, GR_GL_FRAMEBUFFER, kSrc_TempFBOTarget);
      GrGLTexture* dstTex = static_cast<GrGLTexture *>(dst->asTexture());
      SkASSERT(dstTex);
      // We modified the bound FBO
      fHWBoundRenderTargetUniqueID.makeInvalid();
  
      this->bindTextureToScratchUnit(dstTex->target(), dstTex->textureID());
      GL_CALL(CopyTexSubImage2D(dstTex->target(), 0,
                                dstPoint.fX, dstPoint.fY,
                                srcRect.fLeft, srcRect.fTop,
                                srcRect.width(), srcRect.height()));
      this->unbindSurfaceFBOForPixelOps(src, 0, GR_GL_FRAMEBUFFER);
      SkIRect dstRect = SkIRect::MakeXYWH(dstPoint.fX, dstPoint.fY,
                                          srcRect.width(), srcRect.height());
      // The rect is already in device space so we pass in kTopLeft so no flip is done.
      this->didWriteToSurface(dst, kTopLeft_GrSurfaceOrigin, &dstRect);
  }
  
  bool GrGLGpu::copySurfaceAsBlitFramebuffer(GrSurface* dst, GrSurface* src, const SkIRect& srcRect,
                                             const SkIPoint& dstPoint) {
      SkASSERT(can_blit_framebuffer_for_copy_surface(dst, src, srcRect, dstPoint, this->glCaps()));
      SkIRect dstRect = SkIRect::MakeXYWH(dstPoint.fX, dstPoint.fY,
                                          srcRect.width(), srcRect.height());
      if (dst == src) {
          if (SkIRect::Intersects(dstRect, srcRect)) {
              return false;
          }
      }
  
      this->bindSurfaceFBOForPixelOps(dst, 0, GR_GL_DRAW_FRAMEBUFFER, kDst_TempFBOTarget);
      this->bindSurfaceFBOForPixelOps(src, 0, GR_GL_READ_FRAMEBUFFER, kSrc_TempFBOTarget);
      // We modified the bound FBO
      fHWBoundRenderTargetUniqueID.makeInvalid();
  
      // BlitFrameBuffer respects the scissor, so disable it.
      this->disableScissor();
      this->disableWindowRectangles();
  
      GL_CALL(BlitFramebuffer(srcRect.fLeft,
                              srcRect.fTop,
                              srcRect.fRight,
                              srcRect.fBottom,
                              dstRect.fLeft,
                              dstRect.fTop,
                              dstRect.fRight,
                              dstRect.fBottom,
                              GR_GL_COLOR_BUFFER_BIT, GR_GL_NEAREST));
      this->unbindSurfaceFBOForPixelOps(dst, 0, GR_GL_DRAW_FRAMEBUFFER);
      this->unbindSurfaceFBOForPixelOps(src, 0, GR_GL_READ_FRAMEBUFFER);
  
      // The rect is already in device space so we pass in kTopLeft so no flip is done.
      this->didWriteToSurface(dst, kTopLeft_GrSurfaceOrigin, &dstRect);
      return true;
  }
  
  bool GrGLGpu::onRegenerateMipMapLevels(GrTexture* texture) {
      auto glTex = static_cast<GrGLTexture*>(texture);
      // Mipmaps are only supported on 2D textures:
      if (GR_GL_TEXTURE_2D != glTex->target()) {
          return false;
      }
      GrGLFormat format = glTex->format();
      // Manual implementation of mipmap generation, to work around driver bugs w/sRGB.
      // Uses draw calls to do a series of downsample operations to successive mips.
  
      // The manual approach requires the ability to limit which level we're sampling and that the
      // destination can be bound to a FBO:
      if (!this->glCaps().doManualMipmapping() || !this->glCaps().isFormatRenderable(format, 1)) {
          GrGLenum target = glTex->target();
          this->bindTextureToScratchUnit(target, glTex->textureID());
          GL_CALL(GenerateMipmap(glTex->target()));
          return true;
      }
  
      int width = texture->width();
      int height = texture->height();
      int levelCount = SkMipMap::ComputeLevelCount(width, height) + 1;
      SkASSERT(levelCount == texture->texturePriv().maxMipMapLevel() + 1);
  
      // Create (if necessary), then bind temporary FBO:
      if (0 == fTempDstFBOID) {
          GL_CALL(GenFramebuffers(1, &fTempDstFBOID));
      }
      this->bindFramebuffer(GR_GL_FRAMEBUFFER, fTempDstFBOID);
      fHWBoundRenderTargetUniqueID.makeInvalid();
  
      // Bind the texture, to get things configured for filtering.
      // We'll be changing our base level further below:
      this->setTextureUnit(0);
      // The mipmap program does not do any swizzling.
      this->bindTexture(0, GrSamplerState::ClampBilerp(), GrSwizzle::RGBA(), glTex);
  
      // Vertex data:
      if (!fMipmapProgramArrayBuffer) {
          static const GrGLfloat vdata[] = {
              0, 0,
              0, 1,
              1, 0,
              1, 1
          };
          fMipmapProgramArrayBuffer = GrGLBuffer::Make(this, sizeof(vdata), GrGpuBufferType::kVertex,
                                                       kStatic_GrAccessPattern, vdata);
      }
      if (!fMipmapProgramArrayBuffer) {
          return false;
      }
  
      fHWVertexArrayState.setVertexArrayID(this, 0);
  
      GrGLAttribArrayState* attribs = fHWVertexArrayState.bindInternalVertexArray(this);
      attribs->enableVertexArrays(this, 1);
      attribs->set(this, 0, fMipmapProgramArrayBuffer.get(), kFloat2_GrVertexAttribType,
                   kFloat2_GrSLType, 2 * sizeof(GrGLfloat), 0);
  
      // Set "simple" state once:
      this->flushBlendAndColorWrite(GrXferProcessor::BlendInfo(), GrSwizzle::RGBA());
      this->flushHWAAState(nullptr, false);
      this->disableScissor();
      this->disableWindowRectangles();
      this->disableStencil();
  
      // Do all the blits:
      width = texture->width();
      height = texture->height();
  
      for (GrGLint level = 1; level < levelCount; ++level) {
          // Get and bind the program for this particular downsample (filter shape can vary):
          int progIdx = TextureSizeToMipmapProgramIdx(width, height);
          if (!fMipmapPrograms[progIdx].fProgram) {
              if (!this->createMipmapProgram(progIdx)) {
                  SkDebugf("Failed to create mipmap program.\n");
                  // Invalidate all params to cover base level change in a previous iteration.
                  glTex->textureParamsModified();
                  return false;
              }
          }
          this->flushProgram(fMipmapPrograms[progIdx].fProgram);
  
          // Texcoord uniform is expected to contain (1/w, (w-1)/w, 1/h, (h-1)/h)
          const float invWidth = 1.0f / width;
          const float invHeight = 1.0f / height;
          GL_CALL(Uniform4f(fMipmapPrograms[progIdx].fTexCoordXformUniform,
                            invWidth, (width - 1) * invWidth, invHeight, (height - 1) * invHeight));
          GL_CALL(Uniform1i(fMipmapPrograms[progIdx].fTextureUniform, 0));
  
          // Only sample from previous mip
          GL_CALL(TexParameteri(GR_GL_TEXTURE_2D, GR_GL_TEXTURE_BASE_LEVEL, level - 1));
  
          GL_CALL(FramebufferTexture2D(GR_GL_FRAMEBUFFER, GR_GL_COLOR_ATTACHMENT0, GR_GL_TEXTURE_2D,
                                       glTex->textureID(), level));
  
          width = SkTMax(1, width / 2);
          height = SkTMax(1, height / 2);
          this->flushViewport(width, height);
  
          GL_CALL(DrawArrays(GR_GL_TRIANGLE_STRIP, 0, 4));
      }
  
      // Unbind:
      GL_CALL(FramebufferTexture2D(GR_GL_FRAMEBUFFER, GR_GL_COLOR_ATTACHMENT0,
                                   GR_GL_TEXTURE_2D, 0, 0));
  
      // We modified the base level param.
      GrGLTextureParameters::NonsamplerState nonsamplerState = glTex->parameters()->nonsamplerState();
      // We drew the 2nd to last level into the last level.
      nonsamplerState.fBaseMipMapLevel = levelCount - 2;
      glTex->parameters()->set(nullptr, nonsamplerState, fResetTimestampForTextureParameters);
  
      return true;
  }
  
  void GrGLGpu::querySampleLocations(
          GrRenderTarget* renderTarget, SkTArray<SkPoint>* sampleLocations) {
      this->flushRenderTargetNoColorWrites(static_cast<GrGLRenderTarget*>(renderTarget));
  
      int effectiveSampleCnt;
      GR_GL_GetIntegerv(this->glInterface(), GR_GL_SAMPLES, &effectiveSampleCnt);
      SkASSERT(effectiveSampleCnt >= renderTarget->numSamples());
  
      sampleLocations->reset(effectiveSampleCnt);
      for (int i = 0; i < effectiveSampleCnt; ++i) {
          GL_CALL(GetMultisamplefv(GR_GL_SAMPLE_POSITION, i, &(*sampleLocations)[i].fX));
      }
  }
  
  void GrGLGpu::xferBarrier(GrRenderTarget* rt, GrXferBarrierType type) {
      SkASSERT(type);
      switch (type) {
          case kTexture_GrXferBarrierType: {
              GrGLRenderTarget* glrt = static_cast<GrGLRenderTarget*>(rt);
              SkASSERT(glrt->textureFBOID() != 0 && glrt->renderFBOID() != 0);
              if (glrt->textureFBOID() != glrt->renderFBOID()) {
                  // The render target uses separate storage so no need for glTextureBarrier.
                  // FIXME: The render target will resolve automatically when its texture is bound,
                  // but we could resolve only the bounds that will be read if we do it here instead.
                  return;
              }
              SkASSERT(this->caps()->textureBarrierSupport());
              GL_CALL(TextureBarrier());
              return;
          }
          case kBlend_GrXferBarrierType:
              SkASSERT(GrCaps::kAdvanced_BlendEquationSupport ==
                       this->caps()->blendEquationSupport());
              GL_CALL(BlendBarrier());
              return;
          default: break; // placate compiler warnings that kNone not handled
      }
  }
  
  static GrPixelConfig gl_format_to_pixel_config(GrGLFormat format) {
      switch (format) {
          case GrGLFormat::kRGBA8:                return kRGBA_8888_GrPixelConfig;
          case GrGLFormat::kRGB8:                 return kRGB_888_GrPixelConfig;
          case GrGLFormat::kRG8:                  return kRG_88_GrPixelConfig;
          case GrGLFormat::kBGRA8:                return kBGRA_8888_GrPixelConfig;
          case GrGLFormat::kLUMINANCE8:           return kGray_8_GrPixelConfig;
          case GrGLFormat::kSRGB8_ALPHA8:         return kSRGBA_8888_GrPixelConfig;
          case GrGLFormat::kRGB10_A2:             return kRGBA_1010102_GrPixelConfig;
          case GrGLFormat::kRGB565:               return kRGB_565_GrPixelConfig;
          case GrGLFormat::kRGBA4:                return kRGBA_4444_GrPixelConfig;
          case GrGLFormat::kRGBA16F:              return kRGBA_half_GrPixelConfig;
          case GrGLFormat::kR16:                  return kAlpha_16_GrPixelConfig;
          case GrGLFormat::kRG16:                 return kRG_1616_GrPixelConfig;
          case GrGLFormat::kRGBA16:               return kRGBA_16161616_GrPixelConfig;
          case GrGLFormat::kRG16F:                return kRG_half_GrPixelConfig;
          case GrGLFormat::kUnknown:              return kUnknown_GrPixelConfig;
  
          // Configs with multiple equivalent formats.
  
          case GrGLFormat::kR16F:                 return kAlpha_half_GrPixelConfig;
          case GrGLFormat::kLUMINANCE16F:         return kAlpha_half_GrPixelConfig;
  
          case GrGLFormat::kALPHA8:               return kAlpha_8_GrPixelConfig;
          case GrGLFormat::kR8:                   return kAlpha_8_GrPixelConfig;
  
          case GrGLFormat::kCOMPRESSED_RGB8_ETC2: return kRGB_ETC1_GrPixelConfig;
          case GrGLFormat::kCOMPRESSED_ETC1_RGB8: return kRGB_ETC1_GrPixelConfig;
      }
      SkUNREACHABLE;
  }
  
  GrBackendTexture GrGLGpu::onCreateBackendTexture(int w, int h,
                                                   const GrBackendFormat& format,
                                                   GrMipMapped mipMapped,
                                                   GrRenderable renderable,
                                                   const SkPixmap srcData[], int numMipLevels,
                                                   const SkColor4f* color,
                                                   GrProtected isProtected) {
      this->handleDirtyContext();
  
      SkDEBUGCODE(const GrCaps* caps = this->caps();)
  
      // GrGpu::createBackendTexture should've ensured these conditions
      SkASSERT(w >= 1 && w <= caps->maxTextureSize() && h >= 1 && h <= caps->maxTextureSize());
      SkASSERT(GrGpu::MipMapsAreCorrect(w, h, mipMapped, srcData, numMipLevels));
      SkASSERT(mipMapped == GrMipMapped::kNo || caps->mipMapSupport());
  
      GrGLFormat glFormat = format.asGLFormat();
      if (glFormat == GrGLFormat::kUnknown) {
          return GrBackendTexture();  // invalid
      }
  
      // Compressed formats go through onCreateCompressedBackendTexture
      SkASSERT(!GrGLFormatIsCompressed(glFormat));
  
      GrPixelConfig config = gl_format_to_pixel_config(glFormat);
  
      if (config == kUnknown_GrPixelConfig) {
          return GrBackendTexture();  // invalid
      }
  
      auto textureColorType = GrPixelConfigToColorType(config);
  
      // TODO: move the texturability check up to GrGpu::createBackendTexture and just assert here
      if (!this->caps()->isFormatTexturableAndUploadable(textureColorType, format)) {
          return GrBackendTexture();  // invalid
      }
  
      GrGLTextureInfo info;
      GrGLTextureParameters::SamplerOverriddenState initialState;
  
      SkTDArray<GrMipLevel> texels;
      SkAutoMalloc pixelStorage;
  
      int mipLevelCount = 1;
      if (srcData) {
          mipLevelCount = numMipLevels;
          texels.append(mipLevelCount);
          for (int i = 0; i < mipLevelCount; ++i) {
              texels[i] = { srcData[i].addr(), srcData[i].rowBytes() };
          }
      } else if (color) {
          if (GrMipMapped::kYes == mipMapped) {
              mipLevelCount = SkMipMap::ComputeLevelCount(w, h) + 1;
          }
  
          texels.append(mipLevelCount);
          SkTArray<size_t> individualMipOffsets(mipLevelCount);
  
          size_t bytesPerPixel = this->glCaps().bytesPerPixel(glFormat);
  
          size_t totalSize = GrComputeTightCombinedBufferSize(
                  bytesPerPixel, w, h, &individualMipOffsets, mipLevelCount);
  
          char* tmpPixels = (char*)pixelStorage.reset(totalSize);
  
          GrFillInData(textureColorType, w, h, individualMipOffsets, tmpPixels, *color);
          for (int i = 0; i < mipLevelCount; ++i) {
              size_t offset = individualMipOffsets[i];
  
              int twoToTheMipLevel = 1 << i;
              int currentWidth = SkTMax(1, w / twoToTheMipLevel);
  
              texels[i] = {&(tmpPixels[offset]), currentWidth * bytesPerPixel};
          }
      }
  
      GrSurfaceDesc desc;
      desc.fWidth = w;
      desc.fHeight = h;
      desc.fConfig = config;
  
      info.fTarget = GR_GL_TEXTURE_2D;
      info.fFormat = GrGLFormatToEnum(glFormat);
      info.fID = this->createTexture2D({desc.fWidth, desc.fHeight}, glFormat, renderable,
                                       &initialState, SkTMax(1, texels.count()));
      if (!info.fID) {
          return GrBackendTexture();  // invalid
      }
      auto srcColorType = GrPixelConfigToColorType(desc.fConfig);
      if (!texels.empty() &&
          !this->uploadTexData(glFormat, textureColorType, desc.fWidth, desc.fHeight,
                               GR_GL_TEXTURE_2D, 0, 0, desc.fWidth, desc.fHeight, srcColorType,
                               texels.begin(), texels.count())) {
          GL_CALL(DeleteTextures(1, &info.fID));
          return GrBackendTexture();
      }
  
      // unbind the texture from the texture unit to avoid asserts
      GL_CALL(BindTexture(info.fTarget, 0));
  
      auto parameters = sk_make_sp<GrGLTextureParameters>();
      parameters->set(&initialState, GrGLTextureParameters::NonsamplerState(),
                      fResetTimestampForTextureParameters);
  
      return GrBackendTexture(w, h, mipMapped, info, std::move(parameters));
  }
  
  void GrGLGpu::deleteBackendTexture(const GrBackendTexture& tex) {
      SkASSERT(GrBackendApi::kOpenGL == tex.backend());
  
      GrGLTextureInfo info;
      if (tex.getGLTextureInfo(&info)) {
          GL_CALL(DeleteTextures(1, &info.fID));
      }
  }
  
  #if GR_TEST_UTILS
  
  bool GrGLGpu::isTestingOnlyBackendTexture(const GrBackendTexture& tex) const {
      SkASSERT(GrBackendApi::kOpenGL == tex.backend());
  
      GrGLTextureInfo info;
      if (!tex.getGLTextureInfo(&info)) {
          return false;
      }
  
      GrGLboolean result;
      GL_CALL_RET(result, IsTexture(info.fID));
  
      return (GR_GL_TRUE == result);
  }
  
  GrBackendRenderTarget GrGLGpu::createTestingOnlyBackendRenderTarget(int w, int h,
                                                                      GrColorType colorType) {
      if (w > this->caps()->maxRenderTargetSize() || h > this->caps()->maxRenderTargetSize()) {
          return GrBackendRenderTarget();  // invalid
      }
      this->handleDirtyContext();
      auto format = this->glCaps().getFormatFromColorType(colorType);
      if (!this->glCaps().isFormatRenderable(format, 1)) {
          return {};
      }
      bool useTexture = format == GrGLFormat::kBGRA8;
      int sFormatIdx = this->getCompatibleStencilIndex(format);
      if (sFormatIdx < 0) {
          return {};
      }
      GrGLuint colorID = 0;
      GrGLuint stencilID = 0;
      auto deleteIDs = [&] {
          if (colorID) {
              if (useTexture) {
                  GL_CALL(DeleteTextures(1, &colorID));
              } else {
                  GL_CALL(DeleteRenderbuffers(1, &colorID));
              }
          }
          if (stencilID) {
              GL_CALL(DeleteRenderbuffers(1, &stencilID));
          }
      };
  
      if (useTexture) {
          GL_CALL(GenTextures(1, &colorID));
      } else {
          GL_CALL(GenRenderbuffers(1, &colorID));
      }
      GL_CALL(GenRenderbuffers(1, &stencilID));
      if (!stencilID || !colorID) {
          deleteIDs();
          return {};
      }
  
      GrGLFramebufferInfo info;
      info.fFBOID = 0;
      info.fFormat = GrGLFormatToEnum(format);
      GL_CALL(GenFramebuffers(1, &info.fFBOID));
      if (!info.fFBOID) {
          deleteIDs();
          return {};
      }
  
      this->invalidateBoundRenderTarget();
  
      this->bindFramebuffer(GR_GL_FRAMEBUFFER, info.fFBOID);
      if (useTexture) {
          GrGLTextureParameters::SamplerOverriddenState initialState;
          colorID = this->createTexture2D({w, h}, format, GrRenderable::kYes, &initialState, 1);
          if (!colorID) {
              deleteIDs();
              return {};
          }
          GL_CALL(FramebufferTexture2D(GR_GL_FRAMEBUFFER, GR_GL_COLOR_ATTACHMENT0, GR_GL_TEXTURE_2D,
                                       colorID, 0));
      } else {
          GrGLenum renderBufferFormat = this->glCaps().getRenderbufferInternalFormat(format);
          GL_CALL(BindRenderbuffer(GR_GL_RENDERBUFFER, colorID));
          GL_ALLOC_CALL(this->glInterface(),
                        RenderbufferStorage(GR_GL_RENDERBUFFER, renderBufferFormat, w, h));
          GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER, GR_GL_COLOR_ATTACHMENT0,
                                          GR_GL_RENDERBUFFER, colorID));
      }
      GL_CALL(BindRenderbuffer(GR_GL_RENDERBUFFER, stencilID));
      auto stencilBufferFormat = this->glCaps().stencilFormats()[sFormatIdx].fInternalFormat;
      GL_ALLOC_CALL(this->glInterface(),
                    RenderbufferStorage(GR_GL_RENDERBUFFER, stencilBufferFormat, w, h));
      GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER, GR_GL_STENCIL_ATTACHMENT, GR_GL_RENDERBUFFER,
                                      stencilID));
      if (this->glCaps().stencilFormats()[sFormatIdx].fPacked) {
          GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER, GR_GL_DEPTH_ATTACHMENT,
                                          GR_GL_RENDERBUFFER, stencilID));
      }
  
      // We don't want to have to recover the renderbuffer/texture IDs later to delete them. OpenGL
      // has this rule that if a renderbuffer/texture is deleted and a FBO other than the current FBO
      // has the RB attached then deletion is delayed. So we unbind the FBO here and delete the
      // renderbuffers/texture.
      this->bindFramebuffer(GR_GL_FRAMEBUFFER, 0);
      deleteIDs();
  
      this->bindFramebuffer(GR_GL_FRAMEBUFFER, info.fFBOID);
      GrGLenum status;
      GL_CALL_RET(status, CheckFramebufferStatus(GR_GL_FRAMEBUFFER));
      if (GR_GL_FRAMEBUFFER_COMPLETE != status) {
          this->deleteFramebuffer(info.fFBOID);
          return {};
      }
      auto stencilBits = SkToInt(this->glCaps().stencilFormats()[sFormatIdx].fStencilBits);
  
      GrBackendRenderTarget beRT = GrBackendRenderTarget(w, h, 1, stencilBits, info);
      SkASSERT(this->caps()->areColorTypeAndFormatCompatible(colorType, beRT.getBackendFormat()));
      return beRT;
  }
  
  void GrGLGpu::deleteTestingOnlyBackendRenderTarget(const GrBackendRenderTarget& backendRT) {
      SkASSERT(GrBackendApi::kOpenGL == backendRT.backend());
      GrGLFramebufferInfo info;
      if (backendRT.getGLFramebufferInfo(&info)) {
          if (info.fFBOID) {
              this->deleteFramebuffer(info.fFBOID);
          }
      }
  }
  
  void GrGLGpu::testingOnly_flushGpuAndSync() {
      GL_CALL(Finish());
  }
  #endif
  
  ///////////////////////////////////////////////////////////////////////////////
  
  GrGLAttribArrayState* GrGLGpu::HWVertexArrayState::bindInternalVertexArray(GrGLGpu* gpu,
                                                                             const GrBuffer* ibuf) {
      GrGLAttribArrayState* attribState;
  
      if (gpu->glCaps().isCoreProfile()) {
          if (!fCoreProfileVertexArray) {
              GrGLuint arrayID;
              GR_GL_CALL(gpu->glInterface(), GenVertexArrays(1, &arrayID));
              int attrCount = gpu->glCaps().maxVertexAttributes();
              fCoreProfileVertexArray = new GrGLVertexArray(arrayID, attrCount);
          }
          if (ibuf) {
              attribState = fCoreProfileVertexArray->bindWithIndexBuffer(gpu, ibuf);
          } else {
              attribState = fCoreProfileVertexArray->bind(gpu);
          }
      } else {
          if (ibuf) {
              // bindBuffer implicitly binds VAO 0 when binding an index buffer.
              gpu->bindBuffer(GrGpuBufferType::kIndex, ibuf);
          } else {
              this->setVertexArrayID(gpu, 0);
          }
          int attrCount = gpu->glCaps().maxVertexAttributes();
          if (fDefaultVertexArrayAttribState.count() != attrCount) {
              fDefaultVertexArrayAttribState.resize(attrCount);
          }
          attribState = &fDefaultVertexArrayAttribState;
      }
      return attribState;
  }
  
  void GrGLGpu::onFinishFlush(GrSurfaceProxy*[], int, SkSurface::BackendSurfaceAccess access,
                              const GrFlushInfo& info, const GrPrepareForExternalIORequests&) {
      // If we inserted semaphores during the flush, we need to call GLFlush.
      bool insertedSemaphore = info.fNumSemaphores > 0 && this->caps()->semaphoreSupport();
      // We call finish if the client told us to sync or if we have a finished proc but don't support
      // GLsync objects.
      bool finish = (info.fFlags & kSyncCpu_GrFlushFlag) ||
                    (info.fFinishedProc && !this->caps()->fenceSyncSupport());
      if (finish) {
          GL_CALL(Finish());
          // After a finish everything previously sent to GL is done.
          for (const auto& cb : fFinishCallbacks) {
              cb.fCallback(cb.fContext);
              this->deleteSync(cb.fSync);
          }
          fFinishCallbacks.clear();
          if (info.fFinishedProc) {
              info.fFinishedProc(info.fFinishedContext);
          }
      } else {
          if (info.fFinishedProc) {
              FinishCallback callback;
              callback.fCallback = info.fFinishedProc;
              callback.fContext = info.fFinishedContext;
              callback.fSync = (GrGLsync)this->insertFence();
              fFinishCallbacks.push_back(callback);
              GL_CALL(Flush());
          } else if (insertedSemaphore) {
              // Must call flush after semaphores in case they are waited on another GL context.
              GL_CALL(Flush());
          }
          // See if any previously inserted finish procs are good to go.
          this->checkFinishProcs();
      }
  }
  
  void GrGLGpu::submit(GrOpsRenderPass* renderPass) {
      // The GrGLOpsRenderPass doesn't buffer ops so there is nothing to do here
      SkASSERT(fCachedOpsRenderPass.get() == renderPass);
      fCachedOpsRenderPass->reset();
  }
  
  GrFence SK_WARN_UNUSED_RESULT GrGLGpu::insertFence() {
      SkASSERT(this->caps()->fenceSyncSupport());
      GrGLsync sync;
      GL_CALL_RET(sync, FenceSync(GR_GL_SYNC_GPU_COMMANDS_COMPLETE, 0));
      GR_STATIC_ASSERT(sizeof(GrFence) >= sizeof(GrGLsync));
      return (GrFence)sync;
  }
  
  bool GrGLGpu::waitSync(GrGLsync sync, uint64_t timeout, bool flush) {
      GrGLbitfield flags = flush ? GR_GL_SYNC_FLUSH_COMMANDS_BIT : 0;
      GrGLenum result;
      GL_CALL_RET(result, ClientWaitSync(sync, flags, timeout));
      return (GR_GL_CONDITION_SATISFIED == result || GR_GL_ALREADY_SIGNALED == result);
  }
  
  bool GrGLGpu::waitFence(GrFence fence, uint64_t timeout) {
      return this->waitSync((GrGLsync)fence, timeout, /* flush = */ true);
  }
  
  void GrGLGpu::deleteFence(GrFence fence) const {
      this->deleteSync((GrGLsync)fence);
  }
  
  sk_sp<GrSemaphore> SK_WARN_UNUSED_RESULT GrGLGpu::makeSemaphore(bool isOwned) {
      SkASSERT(this->caps()->semaphoreSupport());
      return GrGLSemaphore::Make(this, isOwned);
  }
  
  sk_sp<GrSemaphore> GrGLGpu::wrapBackendSemaphore(const GrBackendSemaphore& semaphore,
                                                   GrResourceProvider::SemaphoreWrapType wrapType,
                                                   GrWrapOwnership ownership) {
      SkASSERT(this->caps()->semaphoreSupport());
      return GrGLSemaphore::MakeWrapped(this, semaphore.glSync(), ownership);
  }
  
  void GrGLGpu::insertSemaphore(sk_sp<GrSemaphore> semaphore) {
      GrGLSemaphore* glSem = static_cast<GrGLSemaphore*>(semaphore.get());
  
      GrGLsync sync;
      GL_CALL_RET(sync, FenceSync(GR_GL_SYNC_GPU_COMMANDS_COMPLETE, 0));
      glSem->setSync(sync);
  }
  
  void GrGLGpu::waitSemaphore(sk_sp<GrSemaphore> semaphore) {
      GrGLSemaphore* glSem = static_cast<GrGLSemaphore*>(semaphore.get());
  
      GL_CALL(WaitSync(glSem->sync(), 0, GR_GL_TIMEOUT_IGNORED));
  }
  
  void GrGLGpu::checkFinishProcs() {
      // Bail after the first unfinished sync since we expect they signal in the order inserted.
      while (!fFinishCallbacks.empty() && this->waitSync(fFinishCallbacks.front().fSync,
                                                         /* timeout = */ 0, /* flush  = */ false)) {
          fFinishCallbacks.front().fCallback(fFinishCallbacks.front().fContext);
          this->deleteSync(fFinishCallbacks.front().fSync);
          fFinishCallbacks.pop_front();
      }
  }
  
  void GrGLGpu::deleteSync(GrGLsync sync) const {
      GL_CALL(DeleteSync(sync));
  }
  
  void GrGLGpu::insertEventMarker(const char* msg) {
      GL_CALL(InsertEventMarker(strlen(msg), msg));
  }
  
  sk_sp<GrSemaphore> GrGLGpu::prepareTextureForCrossContextUsage(GrTexture* texture) {
      // Set up a semaphore to be signaled once the data is ready, and flush GL
      sk_sp<GrSemaphore> semaphore = this->makeSemaphore(true);
      this->insertSemaphore(semaphore);
      // We must call flush here to make sure the GrGLSync object gets created and sent to the gpu.
      GL_CALL(Flush());
  
      return semaphore;
  }
  
  int GrGLGpu::TextureToCopyProgramIdx(GrTexture* texture) {
      switch (GrSLCombinedSamplerTypeForTextureType(texture->texturePriv().textureType())) {
          case kTexture2DSampler_GrSLType:
              return 0;
          case kTexture2DRectSampler_GrSLType:
              return 1;
          case kTextureExternalSampler_GrSLType:
              return 2;
          default:
              SK_ABORT("Unexpected samper type");
      }
  }
  
  #ifdef SK_ENABLE_DUMP_GPU
  #include "src/utils/SkJSONWriter.h"
  void GrGLGpu::onDumpJSON(SkJSONWriter* writer) const {
      // We are called by the base class, which has already called beginObject(). We choose to nest
      // all of our caps information in a named sub-object.
      writer->beginObject("GL GPU");
  
      const GrGLubyte* str;
      GL_CALL_RET(str, GetString(GR_GL_VERSION));
      writer->appendString("GL_VERSION", (const char*)(str));
      GL_CALL_RET(str, GetString(GR_GL_RENDERER));
      writer->appendString("GL_RENDERER", (const char*)(str));
      GL_CALL_RET(str, GetString(GR_GL_VENDOR));
      writer->appendString("GL_VENDOR", (const char*)(str));
      GL_CALL_RET(str, GetString(GR_GL_SHADING_LANGUAGE_VERSION));
      writer->appendString("GL_SHADING_LANGUAGE_VERSION", (const char*)(str));
  
      writer->appendName("extensions");
      glInterface()->fExtensions.dumpJSON(writer);
  
      writer->endObject();
  }
  #endif
  