/*

 * Copyright 2006 The Android Open Source Project

 *

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

 * found in the LICENSE file.

 */

#ifndef SkShader_DEFINED

#define SkShader_DEFINED

#include "include/core/SkBlendMode.h"

#include "include/core/SkColor.h"

#include "include/core/SkFlattenable.h"

#include "include/core/SkImageInfo.h"

#include "include/core/SkMatrix.h"

#include "include/core/SkTileMode.h"

class SkArenaAlloc;

class SkBitmap;

class SkBlender;

class SkColorFilter;

class SkColorSpace;

class SkImage;

class SkPath;

class SkPicture;

class SkRasterPipeline;

class GrFragmentProcessor;

/** \class SkShader

 *

 *  Shaders specify the source color(s) for what is being drawn. If a paint

 *  has no shader, then the paint's color is used. If the paint has a

 *  shader, then the shader's color(s) are use instead, but they are

 *  modulated by the paint's alpha. This makes it easy to create a shader

 *  once (e.g. bitmap tiling or gradient) and then change its transparency

 *  w/o having to modify the original shader... only the paint's alpha needs

 *  to be modified.

 */

class SK_API SkShader : public SkFlattenable {

public:

    /**

     *  Returns true if the shader is guaranteed to produce only opaque

     *  colors, subject to the SkPaint using the shader to apply an opaque

     *  alpha value. Subclasses should override this to allow some

     *  optimizations.

     */

    virtual bool isOpaque() const { return false; }

    /**

     *  Iff this shader is backed by a single SkImage, return its ptr (the caller must ref this

     *  if they want to keep it longer than the lifetime of the shader). If not, return nullptr.

     */

    SkImage* isAImage(SkMatrix* localMatrix, SkTileMode xy[2]) const;

    bool isAImage() const {

        return this->isAImage(nullptr, (SkTileMode*)nullptr) != nullptr;

    }

    /**

     *  If the shader subclass can be represented as a gradient, asAGradient

     *  returns the matching GradientType enum (or kNone_GradientType if it

     *  cannot). Also, if info is not null, asAGradient populates info with

     *  the relevant (see below) parameters for the gradient.  fColorCount

     *  is both an input and output parameter.  On input, it indicates how

     *  many entries in fColors and fColorOffsets can be used, if they are

     *  non-NULL.  After asAGradient has run, fColorCount indicates how

     *  many color-offset pairs there are in the gradient.  If there is

     *  insufficient space to store all of the color-offset pairs, fColors

     *  and fColorOffsets will not be altered.  fColorOffsets specifies

     *  where on the range of 0 to 1 to transition to the given color.

     *  The meaning of fPoint and fRadius is dependant on the type of gradient.

     *

     *  None:

     *      info is ignored.

     *  Color:

     *      fColorOffsets[0] is meaningless.

     *  Linear:

     *      fPoint[0] and fPoint[1] are the end-points of the gradient

     *  Radial:

     *      fPoint[0] and fRadius[0] are the center and radius

     *  Conical:

     *      fPoint[0] and fRadius[0] are the center and radius of the 1st circle

     *      fPoint[1] and fRadius[1] are the center and radius of the 2nd circle

     *  Sweep:

     *      fPoint[0] is the center of the sweep.

     */

    enum GradientType {

        kNone_GradientType,

        kColor_GradientType,

        kLinear_GradientType,

        kRadial_GradientType,

        kSweep_GradientType,

        kConical_GradientType,

        kLast_GradientType = kConical_GradientType,

    };

    struct GradientInfo {

        int         fColorCount;    //!< In-out parameter, specifies passed size

                                    //   of fColors/fColorOffsets on input, and

                                    //   actual number of colors/offsets on

                                    //   output.

        SkColor*    fColors;        //!< The colors in the gradient.

        SkScalar*   fColorOffsets;  //!< The unit offset for color transitions.

        SkPoint     fPoint[2];      //!< Type specific, see above.

        SkScalar    fRadius[2];     //!< Type specific, see above.

        SkTileMode  fTileMode;

        uint32_t    fGradientFlags; //!< see SkGradientShader::Flags

    };

    // DEPRECATED. skbug.com/8941

    virtual GradientType asAGradient(GradientInfo* info) const;

    //////////////////////////////////////////////////////////////////////////

    //  Methods to create combinations or variants of shaders

    /**

     *  Return a shader that will apply the specified localMatrix to this shader.

     *  The specified matrix will be applied before any matrix associated with this shader.

     */

    sk_sp<SkShader> makeWithLocalMatrix(const SkMatrix&) const;

    /**

     *  Create a new shader that produces the same colors as invoking this shader and then applying

     *  the colorfilter.

     */

    sk_sp<SkShader> makeWithColorFilter(sk_sp<SkColorFilter>) const;

private:

    SkShader() = default;

    friend class SkShaderBase;

    using INHERITED = SkFlattenable;

};

class SK_API SkShaders {

public:

    static sk_sp<SkShader> Empty();

    static sk_sp<SkShader> Color(SkColor);

    static sk_sp<SkShader> Color(const SkColor4f&, sk_sp<SkColorSpace>);

    static sk_sp<SkShader> Blend(SkBlendMode mode, sk_sp<SkShader> dst, sk_sp<SkShader> src);

    static sk_sp<SkShader> Blend(sk_sp<SkBlender>, sk_sp<SkShader> dst, sk_sp<SkShader> src);

private:

    SkShaders() = delete;

};

#endif