/*
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* Copyright 2017 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkShaderBase_DEFINED
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#define SkShaderBase_DEFINED
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#include "SkFilterQuality.h"
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#include "SkMask.h"
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#include "SkMatrix.h"
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#include "SkNoncopyable.h"
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#include "SkShader.h"
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#include "SkTLazy.h"
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#if SK_SUPPORT_GPU
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#include "GrFPArgs.h"
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#endif
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class GrContext;
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class GrColorSpaceInfo;
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class GrFragmentProcessor;
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class SkArenaAlloc;
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class SkColorSpace;
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class SkColorSpaceXformer;
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class SkImage;
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struct SkImageInfo;
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class SkPaint;
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class SkRasterPipeline;
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class SkShaderBase : public SkShader {
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public:
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~SkShaderBase() override;
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/**
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* Returns true if the shader is guaranteed to produce only a single color.
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* Subclasses can override this to allow loop-hoisting optimization.
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*/
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virtual bool isConstant() const { return false; }
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const SkMatrix& getLocalMatrix() const { return fLocalMatrix; }
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enum Flags {
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//!< set if all of the colors will be opaque
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kOpaqueAlpha_Flag = 1 << 0,
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/** set if the spans only vary in X (const in Y).
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e.g. an Nx1 bitmap that is being tiled in Y, or a linear-gradient
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that varies from left-to-right. This flag specifies this for
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shadeSpan().
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*/
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kConstInY32_Flag = 1 << 1,
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/** hint for the blitter that 4f is the preferred shading mode.
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*/
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kPrefers4f_Flag = 1 << 2,
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};
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/**
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* ContextRec acts as a parameter bundle for creating Contexts.
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*/
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struct ContextRec {
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ContextRec(const SkPaint& paint, const SkMatrix& matrix, const SkMatrix* localM,
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SkColorType dstColorType, SkColorSpace* dstColorSpace)
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: fPaint(&paint)
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, fMatrix(&matrix)
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, fLocalMatrix(localM)
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, fDstColorType(dstColorType)
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, fDstColorSpace(dstColorSpace) {}
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const SkPaint* fPaint; // the current paint associated with the draw
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const SkMatrix* fMatrix; // the current matrix in the canvas
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const SkMatrix* fLocalMatrix; // optional local matrix
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SkColorType fDstColorType; // the color type of the dest surface
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SkColorSpace* fDstColorSpace; // the color space of the dest surface (if any)
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bool isLegacyCompatible(SkColorSpace* shadersColorSpace) const;
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};
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class Context : public ::SkNoncopyable {
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public:
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Context(const SkShaderBase& shader, const ContextRec&);
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virtual ~Context();
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/**
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* Called sometimes before drawing with this shader. Return the type of
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* alpha your shader will return. The default implementation returns 0.
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* Your subclass should override if it can (even sometimes) report a
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* non-zero value, since that will enable various blitters to perform
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* faster.
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*/
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virtual uint32_t getFlags() const { return 0; }
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/**
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* Called for each span of the object being drawn. Your subclass should
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* set the appropriate colors (with premultiplied alpha) that correspond
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* to the specified device coordinates.
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*/
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virtual void shadeSpan(int x, int y, SkPMColor[], int count) = 0;
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protected:
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// Reference to shader, so we don't have to dupe information.
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const SkShaderBase& fShader;
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uint8_t getPaintAlpha() const { return fPaintAlpha; }
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const SkMatrix& getTotalInverse() const { return fTotalInverse; }
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const SkMatrix& getCTM() const { return fCTM; }
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private:
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SkMatrix fCTM;
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SkMatrix fTotalInverse;
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uint8_t fPaintAlpha;
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typedef SkNoncopyable INHERITED;
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};
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/**
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* Make a context using the memory provided by the arena.
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*
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* @return pointer to context or nullptr if can't be created
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*/
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Context* makeContext(const ContextRec&, SkArenaAlloc*) const;
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#if SK_SUPPORT_GPU
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/**
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* Returns a GrFragmentProcessor that implements the shader for the GPU backend. NULL is
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* returned if there is no GPU implementation.
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*
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* The GPU device does not call SkShader::createContext(), instead we pass the view matrix,
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* local matrix, and filter quality directly.
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*
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* The GrContext may be used by the to create textures that are required by the returned
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* processor.
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*
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* The returned GrFragmentProcessor should expect an unpremultiplied input color and
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* produce a premultiplied output.
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*/
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virtual std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(const GrFPArgs&) const;
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#endif
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/**
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* If the shader can represent its "average" luminance in a single color, return true and
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* if color is not NULL, return that color. If it cannot, return false and ignore the color
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* parameter.
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*
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* Note: if this returns true, the returned color will always be opaque, as only the RGB
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* components are used to compute luminance.
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*/
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bool asLuminanceColor(SkColor*) const;
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/**
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* Returns a shader transformed into a new color space via the |xformer|.
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*/
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sk_sp<SkShader> makeColorSpace(SkColorSpaceXformer* xformer) const {
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return this->onMakeColorSpace(xformer);
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}
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struct StageRec {
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SkRasterPipeline* fPipeline;
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SkArenaAlloc* fAlloc;
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SkColorType fDstColorType;
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SkColorSpace* fDstCS; // may be nullptr
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const SkPaint& fPaint;
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const SkMatrix* fLocalM; // may be nullptr
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SkMatrix fCTM;
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};
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// If this returns false, then we draw nothing (do not fall back to shader context)
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bool appendStages(const StageRec&) const;
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bool SK_WARN_UNUSED_RESULT computeTotalInverse(const SkMatrix& ctm,
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const SkMatrix* outerLocalMatrix,
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SkMatrix* totalInverse) const;
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// Returns the total local matrix for this shader:
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//
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// M = postLocalMatrix x shaderLocalMatrix x preLocalMatrix
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//
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SkTCopyOnFirstWrite<SkMatrix> totalLocalMatrix(const SkMatrix* preLocalMatrix,
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const SkMatrix* postLocalMatrix = nullptr) const;
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virtual SkImage* onIsAImage(SkMatrix*, TileMode[2]) const {
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return nullptr;
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}
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static Type GetFlattenableType() { return kSkShaderBase_Type; }
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Type getFlattenableType() const override { return GetFlattenableType(); }
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static sk_sp<SkShaderBase> Deserialize(const void* data, size_t size,
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const SkDeserialProcs* procs = nullptr) {
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return sk_sp<SkShaderBase>(static_cast<SkShaderBase*>(
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SkFlattenable::Deserialize(GetFlattenableType(), data, size, procs).release()));
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}
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static void RegisterFlattenables();
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protected:
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SkShaderBase(const SkMatrix* localMatrix = nullptr);
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void flatten(SkWriteBuffer&) const override;
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#ifdef SK_ENABLE_LEGACY_SHADERCONTEXT
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/**
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* Specialize creating a SkShader context using the supplied allocator.
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* @return pointer to context owned by the arena allocator.
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*/
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virtual Context* onMakeContext(const ContextRec&, SkArenaAlloc*) const {
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return nullptr;
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}
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/**
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* Overriden by shaders which prefer burst mode.
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*/
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virtual Context* onMakeBurstPipelineContext(const ContextRec&, SkArenaAlloc*) const {
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return nullptr;
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}
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#endif
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virtual bool onAsLuminanceColor(SkColor*) const {
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return false;
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}
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virtual sk_sp<SkShader> onMakeColorSpace(SkColorSpaceXformer*) const {
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return sk_ref_sp(const_cast<SkShaderBase*>(this));
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}
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// Default impl creates shadercontext and calls that (not very efficient)
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virtual bool onAppendStages(const StageRec&) const;
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private:
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// This is essentially const, but not officially so it can be modified in constructors.
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SkMatrix fLocalMatrix;
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typedef SkShader INHERITED;
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};
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inline SkShaderBase* as_SB(SkShader* shader) {
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return static_cast<SkShaderBase*>(shader);
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}
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inline const SkShaderBase* as_SB(const SkShader* shader) {
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return static_cast<const SkShaderBase*>(shader);
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}
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inline const SkShaderBase* as_SB(const sk_sp<SkShader>& shader) {
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return static_cast<SkShaderBase*>(shader.get());
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}
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#endif // SkShaderBase_DEFINED
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