/*

 * Copyright 2017 Google Inc.

 *

 * Use of this source code is governed by a BSD-style license that can be

 * found in the LICENSE file.

 */

#ifndef SkShaderBase_DEFINED

#define SkShaderBase_DEFINED

#include "include/core/SkMatrix.h"

#include "include/core/SkPaint.h"

#include "include/core/SkSamplingOptions.h"

#include "include/core/SkShader.h"

#include "include/private/SkNoncopyable.h"

#include "src/core/SkEffectPriv.h"

#include "src/core/SkMask.h"

#include "src/core/SkTLazy.h"

#include "src/core/SkVM_fwd.h"

#if SK_SUPPORT_GPU

#include "src/gpu/GrFPArgs.h"

#endif

class GrFragmentProcessor;

class SkArenaAlloc;

class SkColorSpace;

class SkImage;

struct SkImageInfo;

class SkPaint;

class SkRasterPipeline;

class SkRuntimeEffect;

/**

 *  Shaders can optionally return a subclass of this when appending their stages.

 *  Doing so tells the caller that the stages can be reused with different CTMs (but nothing

 *  else can change), by calling the updater's udpate() method before each use.

 *

 *  This can be a perf-win bulk draws like drawAtlas and drawVertices, where most of the setup

 *  (i.e. uniforms) are constant, and only something small is changing (i.e. matrices). This

 *  reuse skips the cost of computing the stages (and/or avoids having to allocate a separate

 *  shader for each small draw.

 */

class SkStageUpdater {

public:

    virtual ~SkStageUpdater() {}

    virtual bool SK_WARN_UNUSED_RESULT update(const SkMatrix& ctm) = 0;

};

class SkUpdatableShader;

class SkShaderBase : public SkShader {

public:

    ~SkShaderBase() override;

    sk_sp<SkShader> makeInvertAlpha() const;

    sk_sp<SkShader> makeWithCTM(const SkMatrix&) const;  // owns its own ctm

    /**

     *  Returns true if the shader is guaranteed to produce only a single color.

     *  Subclasses can override this to allow loop-hoisting optimization.

     */

    virtual bool isConstant() const { return false; }

    const SkMatrix& getLocalMatrix() const { return fLocalMatrix; }

    enum Flags {

        //!< set if all of the colors will be opaque

        kOpaqueAlpha_Flag = 1 << 0,

        /** set if the spans only vary in X (const in Y).

            e.g. an Nx1 bitmap that is being tiled in Y, or a linear-gradient

            that varies from left-to-right. This flag specifies this for

            shadeSpan().

         */

        kConstInY32_Flag = 1 << 1,

        /** hint for the blitter that 4f is the preferred shading mode.

         */

        kPrefers4f_Flag  = 1 << 2,

    };

    /**

     *  ContextRec acts as a parameter bundle for creating Contexts.

     */

    struct ContextRec {

        ContextRec(const SkPaint& paint, const SkMatrix& matrix, const SkMatrix* localM,

                   SkColorType dstColorType, SkColorSpace* dstColorSpace)

            : fMatrix(&matrix)

            , fLocalMatrix(localM)

            , fDstColorType(dstColorType)

            , fDstColorSpace(dstColorSpace) {

                fPaintAlpha = paint.getAlpha();

                fPaintDither = paint.isDither();

            }

        const SkMatrix* fMatrix;           // the current matrix in the canvas

        const SkMatrix* fLocalMatrix;      // optional local matrix

        SkColorType     fDstColorType;     // the color type of the dest surface

        SkColorSpace*   fDstColorSpace;    // the color space of the dest surface (if any)

        SkAlpha         fPaintAlpha;

        bool            fPaintDither;

        bool isLegacyCompatible(SkColorSpace* shadersColorSpace) const;

    };

    class Context : public ::SkNoncopyable {

    public:

        Context(const SkShaderBase& shader, const ContextRec&);

        virtual ~Context();

        /**

         *  Called sometimes before drawing with this shader. Return the type of

         *  alpha your shader will return. The default implementation returns 0.

         *  Your subclass should override if it can (even sometimes) report a

         *  non-zero value, since that will enable various blitters to perform

         *  faster.

         */

        virtual uint32_t getFlags() const { return 0; }

        /**

         *  Called for each span of the object being drawn. Your subclass should

         *  set the appropriate colors (with premultiplied alpha) that correspond

         *  to the specified device coordinates.

         */

        virtual void shadeSpan(int x, int y, SkPMColor[], int count) = 0;

    protected:

        // Reference to shader, so we don't have to dupe information.

        const SkShaderBase& fShader;

        uint8_t         getPaintAlpha() const { return fPaintAlpha; }

        const SkMatrix& getTotalInverse() const { return fTotalInverse; }

        const SkMatrix& getCTM() const { return fCTM; }

    private:

        SkMatrix    fCTM;

        SkMatrix    fTotalInverse;

        uint8_t     fPaintAlpha;

        using INHERITED = SkNoncopyable;

    };

    /**

     * Make a context using the memory provided by the arena.

     *

     * @return pointer to context or nullptr if can't be created

     */

    Context* makeContext(const ContextRec&, SkArenaAlloc*) const;

#if SK_SUPPORT_GPU

    /**

     *  Returns a GrFragmentProcessor that implements the shader for the GPU backend. nullptr is

     *  returned if there is no GPU implementation.

     *

     *  The GPU device does not call SkShader::createContext(), instead we pass the view matrix,

     *  local matrix, and filter quality directly.

     *

     *  The GrRecordingContext may be used by the to create textures that are required by the

     *  returned processor.

     *

     *  The returned GrFragmentProcessor should expect an unpremultiplied input color and

     *  produce a premultiplied output.

     */

    virtual std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(const GrFPArgs&) const;

#endif

    /**

     *  If the shader can represent its "average" luminance in a single color, return true and

     *  if color is not NULL, return that color. If it cannot, return false and ignore the color

     *  parameter.

     *

     *  Note: if this returns true, the returned color will always be opaque, as only the RGB

     *  components are used to compute luminance.

     */

    bool asLuminanceColor(SkColor*) const;

    // If this returns false, then we draw nothing (do not fall back to shader context)

    SK_WARN_UNUSED_RESULT

    bool appendStages(const SkStageRec&) const;

    bool SK_WARN_UNUSED_RESULT computeTotalInverse(const SkMatrix& ctm,

                                                   const SkMatrix* outerLocalMatrix,

                                                   SkMatrix* totalInverse) const;

    // Returns the total local matrix for this shader:

    //

    //   M = postLocalMatrix x shaderLocalMatrix x preLocalMatrix

    //

    SkTCopyOnFirstWrite<SkMatrix> totalLocalMatrix(const SkMatrix* preLocalMatrix) const;

    virtual SkImage* onIsAImage(SkMatrix*, SkTileMode[2]) const {

        return nullptr;

    }

    virtual SkRuntimeEffect* asRuntimeEffect() const { return nullptr; }

    static Type GetFlattenableType() { return kSkShader_Type; }

    Type getFlattenableType() const override { return GetFlattenableType(); }

    static sk_sp<SkShaderBase> Deserialize(const void* data, size_t size,

                                             const SkDeserialProcs* procs = nullptr) {

        return sk_sp<SkShaderBase>(static_cast<SkShaderBase*>(

                SkFlattenable::Deserialize(GetFlattenableType(), data, size, procs).release()));

    }

    static void RegisterFlattenables();

    /** DEPRECATED. skbug.com/8941

     *  If this shader can be represented by another shader + a localMatrix, return that shader and

     *  the localMatrix. If not, return nullptr and ignore the localMatrix parameter.

     */

    virtual sk_sp<SkShader> makeAsALocalMatrixShader(SkMatrix* localMatrix) const;

    SkUpdatableShader* updatableShader(SkArenaAlloc* alloc) const;

    virtual SkUpdatableShader* onUpdatableShader(SkArenaAlloc* alloc) const;

    SkStageUpdater* appendUpdatableStages(const SkStageRec& rec) const {

        return this->onAppendUpdatableStages(rec);

    }

    SK_WARN_UNUSED_RESULT

    skvm::Color program(skvm::Builder*, skvm::Coord device, skvm::Coord local, skvm::Color paint,

                        const SkMatrixProvider&, const SkMatrix* localM, const SkColorInfo& dst,

                        skvm::Uniforms* uniforms, SkArenaAlloc* alloc) const;

protected:

    SkShaderBase(const SkMatrix* localMatrix = nullptr);

    void flatten(SkWriteBuffer&) const override;

#ifdef SK_ENABLE_LEGACY_SHADERCONTEXT

    /**

     * Specialize creating a SkShader context using the supplied allocator.

     * @return pointer to context owned by the arena allocator.

     */

    virtual Context* onMakeContext(const ContextRec&, SkArenaAlloc*) const {

        return nullptr;

    }

#endif

    virtual bool onAsLuminanceColor(SkColor*) const {

        return false;

    }

    // Default impl creates shadercontext and calls that (not very efficient)

    virtual bool onAppendStages(const SkStageRec&) const;

    virtual SkStageUpdater* onAppendUpdatableStages(const SkStageRec&) const { return nullptr; }

protected:

    static skvm::Coord ApplyMatrix(skvm::Builder*, const SkMatrix&, skvm::Coord, skvm::Uniforms*);

private:

    // This is essentially const, but not officially so it can be modified in constructors.

    SkMatrix fLocalMatrix;

    virtual skvm::Color onProgram(skvm::Builder*,

                                  skvm::Coord device, skvm::Coord local, skvm::Color paint,

                                  const SkMatrixProvider&, const SkMatrix* localM,

                                  const SkColorInfo& dst, skvm::Uniforms*, SkArenaAlloc*) const = 0;

    using INHERITED = SkShader;

};

class SkUpdatableShader : public SkShaderBase {

public:

    virtual bool update(const SkMatrix& ctm) const = 0;

private:

    // For serialization.  This will never be called.

    Factory getFactory() const override { return nullptr; }

    const char* getTypeName() const override { return nullptr; }

};

inline SkShaderBase* as_SB(SkShader* shader) {

    return static_cast<SkShaderBase*>(shader);

}

inline const SkShaderBase* as_SB(const SkShader* shader) {

    return static_cast<const SkShaderBase*>(shader);

}

inline const SkShaderBase* as_SB(const sk_sp<SkShader>& shader) {

    return static_cast<SkShaderBase*>(shader.get());

}

#endif // SkShaderBase_DEFINED