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 /*

  * 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 SkXfermode_DEFINED

 #define SkXfermode_DEFINED

 #include "SkFlattenable.h"

 #include "SkColor.h"

 class GrEffectRef;

 class GrTexture;

 class SkString;

 /** \class SkXfermode

  *

  *  SkXfermode is the base class for objects that are called to implement custom

  *  "transfer-modes" in the drawing pipeline. The static function Create(Modes)

  *  can be called to return an instance of any of the predefined subclasses as

  *  specified in the Modes enum. When an SkXfermode is assigned to an SkPaint,

  *  then objects drawn with that paint have the xfermode applied.

  *

  *  All subclasses are required to be reentrant-safe : it must be legal to share

  *  the same instance between several threads.

  */

 class SK_API SkXfermode : public SkFlattenable {

 public:

     SK_DECLARE_INST_COUNT(SkXfermode)

     virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count,

                         const SkAlpha aa[]) const;

     virtual void xfer16(uint16_t dst[], const SkPMColor src[], int count,

                         const SkAlpha aa[]) const;

     virtual void xferA8(SkAlpha dst[], const SkPMColor src[], int count,

                         const SkAlpha aa[]) const;

     /** Enum of possible coefficients to describe some xfermodes

      */

     enum Coeff {

         kZero_Coeff,    /** 0 */

         kOne_Coeff,     /** 1 */

         kSC_Coeff,      /** src color */

         kISC_Coeff,     /** inverse src color (i.e. 1 - sc) */

         kDC_Coeff,      /** dst color */

         kIDC_Coeff,     /** inverse dst color (i.e. 1 - dc) */

         kSA_Coeff,      /** src alpha */

         kISA_Coeff,     /** inverse src alpha (i.e. 1 - sa) */

         kDA_Coeff,      /** dst alpha */

         kIDA_Coeff,     /** inverse dst alpha (i.e. 1 - da) */

         kCoeffCount

     };

     /** If the xfermode can be expressed as an equation using the coefficients

         in Coeff, then asCoeff() returns true, and sets (if not null) src and

         dst accordingly.

             result = src_coeff * src_color + dst_coeff * dst_color;

         As examples, here are some of the porterduff coefficients

         MODE        SRC_COEFF       DST_COEFF

         clear       zero            zero

         src         one             zero

         dst         zero            one

         srcover     one             isa

         dstover     ida             one

      */

     virtual bool asCoeff(Coeff* src, Coeff* dst) const;

     /**

      *  The same as calling xfermode->asCoeff(..), except that this also checks

      *  if the xfermode is NULL, and if so, treats it as kSrcOver_Mode.

      */

     static bool AsCoeff(const SkXfermode*, Coeff* src, Coeff* dst);

     /** List of predefined xfermodes.

         The algebra for the modes uses the following symbols:

         Sa, Sc  - source alpha and color

         Da, Dc - destination alpha and color (before compositing)

         [a, c] - Resulting (alpha, color) values

         For these equations, the colors are in premultiplied state.

         If no xfermode is specified, kSrcOver is assumed.

         The modes are ordered by those that can be expressed as a pair of Coeffs, followed by those

         that aren't Coeffs but have separable r,g,b computations, and finally

         those that are not separable.

      */

     enum Mode {

         kClear_Mode,    //!< [0, 0]

         kSrc_Mode,      //!< [Sa, Sc]

         kDst_Mode,      //!< [Da, Dc]

         kSrcOver_Mode,  //!< [Sa + Da - Sa*Da, Rc = Sc + (1 - Sa)*Dc]

         kDstOver_Mode,  //!< [Sa + Da - Sa*Da, Rc = Dc + (1 - Da)*Sc]

         kSrcIn_Mode,    //!< [Sa * Da, Sc * Da]

         kDstIn_Mode,    //!< [Sa * Da, Sa * Dc]

         kSrcOut_Mode,   //!< [Sa * (1 - Da), Sc * (1 - Da)]

         kDstOut_Mode,   //!< [Da * (1 - Sa), Dc * (1 - Sa)]

         kSrcATop_Mode,  //!< [Da, Sc * Da + (1 - Sa) * Dc]

         kDstATop_Mode,  //!< [Sa, Sa * Dc + Sc * (1 - Da)]

         kXor_Mode,      //!< [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + (1 - Sa) * Dc]

         kPlus_Mode,     //!< [Sa + Da, Sc + Dc]

         kModulate_Mode, // multiplies all components (= alpha and color)

         // Following blend modes are defined in the CSS Compositing standard:

         // https://dvcs.w3.org/hg/FXTF/rawfile/tip/compositing/index.html#blending

         kScreen_Mode,

         kLastCoeffMode = kScreen_Mode,

         kOverlay_Mode,

         kDarken_Mode,

         kLighten_Mode,

         kColorDodge_Mode,

         kColorBurn_Mode,

         kHardLight_Mode,

         kSoftLight_Mode,

         kDifference_Mode,

         kExclusion_Mode,

         kMultiply_Mode,

         kLastSeparableMode = kMultiply_Mode,

         kHue_Mode,

         kSaturation_Mode,

         kColor_Mode,

         kLuminosity_Mode,

         kLastMode = kLuminosity_Mode

     };

     /**

      * Gets the name of the Mode as a string.

      */

     static const char* ModeName(Mode);

     /**

      *  If the xfermode is one of the modes in the Mode enum, then asMode()

      *  returns true and sets (if not null) mode accordingly. Otherwise it

      *  returns false and ignores the mode parameter.

      */

     virtual bool asMode(Mode* mode) const;

     /**

      *  The same as calling xfermode->asMode(mode), except that this also checks

      *  if the xfermode is NULL, and if so, treats it as kSrcOver_Mode.

      */

     static bool AsMode(const SkXfermode*, Mode* mode);

     /**

      *  Returns true if the xfermode claims to be the specified Mode. This works

      *  correctly even if the xfermode is NULL (which equates to kSrcOver.) Thus

      *  you can say this without checking for a null...

      *

      *  If (SkXfermode::IsMode(paint.getXfermode(),

      *                         SkXfermode::kDstOver_Mode)) {

      *      ...

      *  }

      */

     static bool IsMode(const SkXfermode* xfer, Mode mode);

     /** Return an SkXfermode object for the specified mode.

      */

     static SkXfermode* Create(Mode mode);

     /** Return a function pointer to a routine that applies the specified

         porter-duff transfer mode.

      */

     static SkXfermodeProc GetProc(Mode mode);

     /** Return a function pointer to a routine that applies the specified

         porter-duff transfer mode and srcColor to a 16bit device color. Note,

         if the mode+srcColor might return a non-opaque color, then there is not

         16bit proc, and this will return NULL.

       */

     static SkXfermodeProc16 GetProc16(Mode mode, SkColor srcColor);

     /**

      *  If the specified mode can be represented by a pair of Coeff, then return

      *  true and set (if not NULL) the corresponding coeffs. If the mode is

      *  not representable as a pair of Coeffs, return false and ignore the

      *  src and dst parameters.

      */

     static bool ModeAsCoeff(Mode mode, Coeff* src, Coeff* dst);

     SK_ATTR_DEPRECATED("use AsMode(...)")

     static bool IsMode(const SkXfermode* xfer, Mode* mode) {

         return AsMode(xfer, mode);

     }

     /** A subclass may implement this factory function to work with the GPU backend. It is legal

         to call this with all params NULL to simply test the return value. If effect is non-NULL

         then the xfermode may optionally allocate an effect to return and the caller as *effect.

         The caller will install it and own a ref to it. Since the xfermode may or may not assign

         *effect, the caller should set *effect to NULL beforehand. background specifies the

         texture to use as the background for compositing, and should be accessed in the effect's

         fragment shader. If NULL, the effect should request access to destination color

         (setWillReadDstColor()), and use that in the fragment shader (builder->dstColor()).

      */

     virtual bool asNewEffect(GrEffectRef** effect, GrTexture* background = NULL) const;

     /** Returns true if the xfermode can be expressed as coeffs (src, dst), or as an effect

         (effect). This helper calls the asCoeff() and asNewEffect() virtuals. If the xfermode is

         NULL, it is treated as kSrcOver_Mode. It is legal to call this with all params NULL to

         simply test the return value.  effect, src, and dst must all be NULL or all non-NULL.

      */

     static bool AsNewEffectOrCoeff(SkXfermode*,

                                    GrEffectRef** effect,

                                    Coeff* src,

                                    Coeff* dst,

                                    GrTexture* background = NULL);

     SK_TO_STRING_PUREVIRT()

     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()

     SK_DEFINE_FLATTENABLE_TYPE(SkXfermode)

 protected:

     SkXfermode(SkReadBuffer& rb) : SkFlattenable(rb) {}

     /** The default implementation of xfer32/xfer16/xferA8 in turn call this

         method, 1 color at a time (upscaled to a SkPMColor). The default

         implmentation of this method just returns dst. If performance is

         important, your subclass should override xfer32/xfer16/xferA8 directly.

         This method will not be called directly by the client, so it need not

         be implemented if your subclass has overridden xfer32/xfer16/xferA8

     */

     virtual SkPMColor xferColor(SkPMColor src, SkPMColor dst) const;

 #ifdef SK_SUPPORT_LEGACY_PUBLICEFFECTCONSTRUCTORS

 public:

 #endif

     SkXfermode() {}

 private:

     enum {

         kModeCount = kLastMode + 1

     };

     friend class SkGraphics;

     static void Term();

     typedef SkFlattenable INHERITED;

 };

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

 /** \class SkProcXfermode

     SkProcXfermode is a xfermode that applies the specified proc to its colors.

     This class is not exported to java.

 */

 class SkProcXfermode : public SkXfermode {

 public:

     static SkProcXfermode* Create(SkXfermodeProc proc) {

         return SkNEW_ARGS(SkProcXfermode, (proc));

     }

     // overrides from SkXfermode

     virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count,

                         const SkAlpha aa[]) const SK_OVERRIDE;

     virtual void xfer16(uint16_t dst[], const SkPMColor src[], int count,

                         const SkAlpha aa[]) const SK_OVERRIDE;

     virtual void xferA8(SkAlpha dst[], const SkPMColor src[], int count,

                         const SkAlpha aa[]) const SK_OVERRIDE;

     SK_TO_STRING_OVERRIDE()

     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkProcXfermode)

 protected:

     SkProcXfermode(SkReadBuffer&);

     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;

     // allow subclasses to update this after we unflatten

     void setProc(SkXfermodeProc proc) {

         fProc = proc;

     }

     SkXfermodeProc getProc() const {

         return fProc;

     }

 #ifdef SK_SUPPORT_LEGACY_PUBLICEFFECTCONSTRUCTORS

 public:

 #endif

     SkProcXfermode(SkXfermodeProc proc) : fProc(proc) {}

 private:

     SkXfermodeProc  fProc;

     typedef SkXfermode INHERITED;

 };

 #endif