make SkXfermode.h go away

This is step one:
- make SkXfermode useless to public clients
- everything they should need is in SkBlendMode.h

Step two:
- remove SkXfermode.h entirely (since skia core will already be using SkXfermodePriv.h)

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4534

Change-Id: If2cea9f71df92430ed6644edb98dd306c5572cbc
Reviewed-on: https://skia-review.googlesource.com/4534
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>

1 files changed, 311 insertions, 0 deletions

diff --git a/src/core/SkXfermodePriv.h b/src/core/SkXfermodePriv.h
new file mode 100644
index 0000000000..b7d85ea98f
--- /dev/null
+++ b/src/core/SkXfermodePriv.h
@@ -0,0 +1,311 @@
+/*
+ * 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 SkXfermodePriv_DEFINED
+#define SkXfermodePriv_DEFINED
+
+#include "SkBlendMode.h"
+#include "SkColor.h"
+#include "SkFlattenable.h"
+
+#ifdef SK_SUPPORT_LEGACY_XFERMODE_IS_PUBLIC
+#include "SkXfermode.h"
+#else
+
+class GrFragmentProcessor;
+class GrTexture;
+class GrXPFactory;
+class SkRasterPipeline;
+class SkString;
+
+struct SkArithmeticParams;
+
+struct SkPM4f;
+typedef SkPM4f (*SkXfermodeProc4f)(const SkPM4f& src, const SkPM4f& dst);
+
+/** \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:
+    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
+    };
+
+    /** 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 * (1 - Sa), Sc + Dc * (1 - Sa)]
+        kDstOver_Mode,  //!< [Da + Sa * (1 - Da), Dc + Sc * (1 - Da)]
+        kSrcIn_Mode,    //!< [Sa * Da, Sc * Da]
+        kDstIn_Mode,    //!< [Da * Sa, Dc * Sa]
+        kSrcOut_Mode,   //!< [Sa * (1 - Da), Sc * (1 - Da)]
+        kDstOut_Mode,   //!< [Da * (1 - Sa), Dc * (1 - Sa)]
+        kSrcATop_Mode,  //!< [Da, Sc * Da + Dc * (1 - Sa)]
+        kDstATop_Mode,  //!< [Sa, Dc * Sa + Sc * (1 - Da)]
+        kXor_Mode,      //!< [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + Dc * (1 - Sa)]
+        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);
+    static const char* ModeName(SkBlendMode mode) {
+        return ModeName(Mode(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);
+    static bool AsMode(const sk_sp<SkXfermode>& xfer, Mode* mode) {
+        return AsMode(xfer.get(), 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);
+    static bool IsMode(const sk_sp<SkXfermode>& xfer, Mode mode) {
+        return IsMode(xfer.get(), mode);
+    }
+
+    /** Return an SkXfermode object for the specified mode.
+     */
+    static sk_sp<SkXfermode> Make(SkBlendMode);
+    static sk_sp<SkXfermode> Make(Mode m) { return Make((SkBlendMode)m); }
+
+    /**
+     *  Skia maintains global xfermode objects corresponding to each BlendMode. This returns a
+     *  ptr to that global xfermode (or null if the mode is srcover). Thus the caller may use
+     *  the returned ptr, but it should leave its refcnt untouched.
+     */
+    static SkXfermode* Peek(SkBlendMode mode) {
+        sk_sp<SkXfermode> xfer = Make(mode);
+        if (!xfer) {
+            SkASSERT(SkBlendMode::kSrcOver == mode);
+            return nullptr;
+        }
+        SkASSERT(!xfer->unique());
+        return xfer.get();
+    }
+
+    SkBlendMode blend() const {
+        Mode mode;
+        SkAssertResult(this->asMode(&mode));
+        return (SkBlendMode)mode;
+    }
+
+    static SkXfermodeProc GetProc(SkBlendMode);
+    static SkXfermodeProc4f GetProc4f(SkBlendMode);
+
+    /**
+     *  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);
+    static bool ModeAsCoeff(SkBlendMode mode, Coeff* src, Coeff* dst) {
+        return ModeAsCoeff((Mode)mode, src, dst);
+    }
+
+    /**
+     * Returns whether or not the xfer mode can support treating coverage as alpha
+     */
+    virtual bool supportsCoverageAsAlpha() const;
+
+    /**
+     *  The same as calling xfermode->supportsCoverageAsAlpha(), except that this also checks if
+     *  the xfermode is NULL, and if so, treats it as kSrcOver_Mode.
+     */
+    static bool SupportsCoverageAsAlpha(const SkXfermode* xfer);
+    static bool SupportsCoverageAsAlpha(const sk_sp<SkXfermode>& xfer) {
+        return SupportsCoverageAsAlpha(xfer.get());
+    }
+
+    enum SrcColorOpacity {
+        // The src color is known to be opaque (alpha == 255)
+        kOpaque_SrcColorOpacity = 0,
+        // The src color is known to be fully transparent (color == 0)
+        kTransparentBlack_SrcColorOpacity = 1,
+        // The src alpha is known to be fully transparent (alpha == 0)
+        kTransparentAlpha_SrcColorOpacity = 2,
+        // The src color opacity is unknown
+        kUnknown_SrcColorOpacity = 3
+    };
+
+    /**
+     * Returns whether or not the result of the draw with the xfer mode will be opaque or not. The
+     * input to this call is an enum describing known information about the opacity of the src color
+     * that will be given to the xfer mode.
+     */
+    virtual bool isOpaque(SrcColorOpacity opacityType) const;
+
+    /**
+     *  The same as calling xfermode->isOpaque(...), except that this also checks if
+     *  the xfermode is NULL, and if so, treats it as kSrcOver_Mode.
+     */
+    static bool IsOpaque(const SkXfermode* xfer, SrcColorOpacity opacityType);
+    static bool IsOpaque(const sk_sp<SkXfermode>& xfer, SrcColorOpacity opacityType) {
+        return IsOpaque(xfer.get(), opacityType);
+    }
+    static bool IsOpaque(SkBlendMode, SrcColorOpacity);
+
+#if SK_SUPPORT_GPU
+    /** Used by the SkXfermodeImageFilter to blend two colors via a GrFragmentProcessor.
+        The input to the returned FP is the src color. The dst color is
+        provided by the dst param which becomes a child FP of the returned FP.
+        It is legal for the function to return a null output. This indicates that
+        the output of the blend is simply the src color.
+     */
+    virtual sk_sp<GrFragmentProcessor> makeFragmentProcessorForImageFilter(
+                                                            sk_sp<GrFragmentProcessor> dst) const;
+
+    /** A subclass must implement this factory function to work with the GPU backend.
+        The xfermode will return a factory for which the caller will get a ref. It is up
+        to the caller to install it. XferProcessors cannot use a background texture.
+      */
+    virtual sk_sp<GrXPFactory> asXPFactory() const;
+#endif
+
+    SK_TO_STRING_PUREVIRT()
+    SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
+    SK_DEFINE_FLATTENABLE_TYPE(SkXfermode)
+
+    enum D32Flags {
+        kSrcIsOpaque_D32Flag  = 1 << 0,
+        kSrcIsSingle_D32Flag  = 1 << 1,
+        kDstIsSRGB_D32Flag    = 1 << 2,
+    };
+    typedef void (*D32Proc)(SkBlendMode, uint32_t dst[], const SkPM4f src[],
+                            int count, const SkAlpha coverage[]);
+    static D32Proc GetD32Proc(SkBlendMode, uint32_t flags);
+
+    enum F16Flags {
+        kSrcIsOpaque_F16Flag  = 1 << 0,
+        kSrcIsSingle_F16Flag  = 1 << 1,
+    };
+    typedef void (*F16Proc)(SkBlendMode, uint64_t dst[], const SkPM4f src[], int count,
+                            const SkAlpha coverage[]);
+    static F16Proc GetF16Proc(SkBlendMode, uint32_t flags);
+
+    enum LCDFlags {
+        kSrcIsOpaque_LCDFlag    = 1 << 0,   // else src(s) may have alpha < 1
+        kSrcIsSingle_LCDFlag    = 1 << 1,   // else src[count]
+        kDstIsSRGB_LCDFlag      = 1 << 2,   // else l32 or f16
+    };
+    typedef void (*LCD32Proc)(uint32_t* dst, const SkPM4f* src, int count, const uint16_t lcd[]);
+    typedef void (*LCDF16Proc)(uint64_t* dst, const SkPM4f* src, int count, const uint16_t lcd[]);
+    static LCD32Proc GetLCD32Proc(uint32_t flags);
+    static LCDF16Proc GetLCDF16Proc(uint32_t) { return nullptr; }
+
+    virtual bool isArithmetic(SkArithmeticParams*) const { return false; }
+
+protected:
+    SkXfermode() {}
+    /** The default implementation of xfer32/xfer16/xferA8 in turn call this
+        method, 1 color at a time (upscaled to a SkPMColor). The default
+        implementation 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;
+
+private:
+    enum {
+        kModeCount = kLastMode + 1
+    };
+
+    typedef SkFlattenable INHERITED;
+};
+
+#endif
+
+#endif