src/sksl/SkSLUtil.h

/*
 * 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 {
        SkASSERT(this->fShaderDerivativeSupport);
        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 {
        SkASSERT(this->fExternalTextureSupport);
        return fExternalTextureExtensionString;
    }

    const char* secondExternalTextureExtensionString() const {
        SkASSERT(this->fExternalTextureSupport);
        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; }

    /**
     * The following group of attributes are only needed for Ganesh/GL. However, we keep there here
     * as opposed to demoting them to being defined in Ganesh's GrShaderCaps for 2 reasons.
     *
     * 1) Some backend-agnostic SkSL utilies reference these capabilities.
     *
     * 2) Even though we do not anticipate Dawn relying upon Skia's GLSL generation for GL support,
     *    sometimes SkSL compilation itself can be impacted by some of these capabilities. Such
     *    attributes will be kept here in case Dawn/GL eventually needs to leverage them.
     */
    bool fFloatIs32Bits = true; /* Queried by SkSLSetting + impacts SkSL generation */
    /**
     * TODO: Modify SkSLGLSLCodeGenerator to use GrShaderCaps rather than this struct since GL
     * should only be used with Ganesh. Once that is complete, the following attribute could be
     * downgraded to GrShaderCaps.
     */
    SkSL::GLSLGeneration fGLSLGeneration = SkSL::GLSLGeneration::k330;
    bool fFlatInterpolationSupport = false; /* Supported by all backends except for some GL impls */
    bool fUsesPrecisionModifiers = false; /* GLSL is the only shading language that uses these */

    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 fNoPerspectiveInterpolationSupport = false;
    bool fSampleMaskSupport = false;
    bool fExternalTextureSupport = false;

    /** isinf() is defined + 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;  // skbug.com/40043167
    /** 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.
     * (skbug.com/40042841)
     */
    bool fRewriteMatrixVectorMultiply = false;
    /** Rewrites matrix equality comparisons to avoid an Adreno driver bug. (skbug.com/40042682) */
    bool fRewriteMatrixComparisons = false;
    /** Strips const from function parameters in the GLSL code generator. (skbug.com/40044949) */
    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;
    /**
     * SPIR-V currently doesn't handle different array strides being passed in to a fixed sized
     * array function parameter, so fForceStd430ArrayLayout will make all array strides conform
     * to std430 stride alignment rules.
     */
    bool fForceStd430ArrayLayout = false;
    /**
     * Some NVIDIA drivers fail to create a pipeline if RelaxedPrecision is applied to
     * OpImageSampleImplicitLod when sampling from a YCbCr image. This workaround simply disables
     * RelaxedPrecision for that op regardless of image kind. (skbug.com/421927604)
     */
    bool fCannotUseRelaxedPrecisionOnImageSample = false;
    /**
     * Clamp, Min, Max, intrinsics all appear to be broken on Intel UHD630, so shaders for these
     * devices will break these intrinsics into individual scalar commands.
     */
    bool fVectorClampMinMaxSupport = true;

    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 {
public:
    static const ShaderCaps* Default() {
        static const SkSL::ShaderCaps* const 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* const sCaps = MakeShaderCaps().release();
        return sCaps;
    }

protected:
    static std::unique_ptr<ShaderCaps> MakeShaderCaps();
};

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