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* Copyright 2016 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SKSL_UTIL
#define SKSL_UTIL
#include "include/core/SkTypes.h"
#include "include/sksl/SkSLVersion.h"
#include "src/sksl/SkSLGLSL.h"
#include <memory>
enum class SkSLType : char;
namespace SkSL {
class Context;
class OutputStream;
class StringStream;
class Type;
struct ShaderCaps {
* Indicates how GLSL must interact with advanced blend equations. The KHR extension requires
* special layout qualifiers in the fragment shader.
enum AdvBlendEqInteraction {
kNotSupported_AdvBlendEqInteraction, //<! No _blend_equation_advanced extension
kAutomatic_AdvBlendEqInteraction, //<! No interaction required
kGeneralEnable_AdvBlendEqInteraction, //<! layout(blend_support_all_equations) out
kLast_AdvBlendEqInteraction = kGeneralEnable_AdvBlendEqInteraction
bool mustEnableAdvBlendEqs() const {
return fAdvBlendEqInteraction >= kGeneralEnable_AdvBlendEqInteraction;
bool mustDeclareFragmentShaderOutput() const {
return fGLSLGeneration > SkSL::GLSLGeneration::k110;
// Returns the string of an extension that must be enabled in the shader to support
// derivatives. If nullptr is returned then no extension needs to be enabled. Before calling
// this function, the caller should check that shaderDerivativeSupport exists.
const char* shaderDerivativeExtensionString() const {
return fShaderDerivativeExtensionString;
// This returns the name of an extension that must be enabled in the shader to support external
// textures. In some cases, two extensions must be enabled - the second extension is returned
// by secondExternalTextureExtensionString(). If that function returns nullptr, then only one
// extension is required.
const char* externalTextureExtensionString() const {
return fExternalTextureExtensionString;
const char* secondExternalTextureExtensionString() const {
return fSecondExternalTextureExtensionString;
* SkSL 300 requires support for derivatives, nonsquare matrices and bitwise integer operations.
SkSL::Version supportedSkSLVerion() const {
if (fShaderDerivativeSupport && fNonsquareMatrixSupport && fIntegerSupport &&
fGLSLGeneration >= SkSL::GLSLGeneration::k330) {
return SkSL::Version::k300;
return SkSL::Version::k100;
bool supportsDistanceFieldText() const { return fShaderDerivativeSupport; }
SkSL::GLSLGeneration fGLSLGeneration = SkSL::GLSLGeneration::k330;
bool fDualSourceBlendingSupport = false;
bool fShaderDerivativeSupport = false;
/** Enables sampleGrad and sampleLod functions that don't rely on implicit derivatives */
bool fExplicitTextureLodSupport = false;
/** Indicates true 32-bit integer support, with unsigned types and bitwise operations */
bool fIntegerSupport = false;
bool fNonsquareMatrixSupport = false;
/** asinh(), acosh(), atanh() */
bool fInverseHyperbolicSupport = false;
bool fFBFetchSupport = false;
bool fFBFetchNeedsCustomOutput = false;
bool fUsesPrecisionModifiers = false;
bool fFlatInterpolationSupport = false;
bool fNoPerspectiveInterpolationSupport = false;
bool fSampleMaskSupport = false;
bool fExternalTextureSupport = false;
bool fFloatIs32Bits = true;
// isinf() is defined, and floating point infinities are handled according to IEEE standards.
bool fInfinitySupport = false;
// Used by SkSL to know when to generate polyfills.
bool fBuiltinFMASupport = true;
bool fBuiltinDeterminantSupport = true;
// Used for specific driver bug work arounds
bool fCanUseVoidInSequenceExpressions = true;
bool fCanUseMinAndAbsTogether = true;
bool fCanUseFractForNegativeValues = true;
bool fMustForceNegatedAtanParamToFloat = false;
bool fMustForceNegatedLdexpParamToMultiply = false; //
// Returns whether a device incorrectly implements atan(y,x) as atan(y/x)
bool fAtan2ImplementedAsAtanYOverX = false;
// If this returns true some operation (could be a no op) must be called between floor and abs
// to make sure the driver compiler doesn't inline them together which can cause a driver bug in
// the shader.
bool fMustDoOpBetweenFloorAndAbs = false;
// The D3D shader compiler, when targeting PS 3.0 (ie within ANGLE) fails to compile certain
// constructs. See detailed comments in GrGLCaps.cpp.
bool fMustGuardDivisionEvenAfterExplicitZeroCheck = false;
// If false, SkSL uses a workaround so that sk_FragCoord doesn't actually query gl_FragCoord
bool fCanUseFragCoord = true;
// If true, then conditions in for loops need "&& true" to work around driver bugs.
bool fAddAndTrueToLoopCondition = false;
// If true, then expressions such as "x && y" or "x || y" are rewritten as ternary to work
// around driver bugs.
bool fUnfoldShortCircuitAsTernary = false;
bool fEmulateAbsIntFunction = false;
bool fRewriteDoWhileLoops = false;
bool fRewriteSwitchStatements = false;
bool fRemovePowWithConstantExponent = false;
// The Android emulator claims samplerExternalOES is an unknown type if a default precision
// statement is made for the type.
bool fNoDefaultPrecisionForExternalSamplers = false;
// ARM GPUs calculate `matrix * vector` in SPIR-V at full precision, even when the inputs are
// RelaxedPrecision. Rewriting the multiply as a sum of vector*scalar fixes this. (skia:11769)
bool fRewriteMatrixVectorMultiply = false;
// Rewrites matrix equality comparisons to avoid an Adreno driver bug. (skia:11308)
bool fRewriteMatrixComparisons = false;
// Strips const from function parameters in the GLSL code generator. (skia:13858)
bool fRemoveConstFromFunctionParameters = false;
// On some Android devices colors aren't accurate enough for the double lookup in the
// Perlin noise shader. This workaround aggressively snaps colors to multiples of 1/255.
bool fPerlinNoiseRoundingFix = false;
// Vulkan requires certain builtin variables be present, even if they're unused. At one time,
// validation errors would result if sk_Clockwise was missing. Now, it's just (Adreno) driver
// bugs that drop or corrupt draws if they're missing.
bool fMustDeclareFragmentFrontFacing = false;
const char* fVersionDeclString = "";
const char* fShaderDerivativeExtensionString = nullptr;
const char* fExternalTextureExtensionString = nullptr;
const char* fSecondExternalTextureExtensionString = nullptr;
const char* fFBFetchColorName = nullptr;
AdvBlendEqInteraction fAdvBlendEqInteraction = kNotSupported_AdvBlendEqInteraction;
// Various sets of caps for use in tests
class ShaderCapsFactory {
static const ShaderCaps* Default() {
static const SkSL::ShaderCaps* sCaps = [] {
std::unique_ptr<ShaderCaps> caps = MakeShaderCaps();
caps->fVersionDeclString = "#version 400";
caps->fShaderDerivativeSupport = true;
return caps.release();
return sCaps;
static const ShaderCaps* Standalone() {
static const SkSL::ShaderCaps* sCaps = MakeShaderCaps().release();
return sCaps;
static std::unique_ptr<ShaderCaps> MakeShaderCaps();
#if !defined(SKSL_STANDALONE) && (defined(SK_GANESH) || defined(SK_GRAPHITE))
bool type_to_sksltype(const Context& context, const Type& type, SkSLType* outType);
void write_stringstream(const StringStream& d, OutputStream& out);
} // namespace SkSL
#endif // SKSL_UTIL