Generic 4f gradient T sampler fallback

src/effects/gradients/Sk4fGradientBase.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef Sk4fGradientBase_DEFINED
 #define Sk4fGradientBase_DEFINED
 
 #include "SkColor.h"
 #include "SkGradientShaderPriv.h"
 #include "SkMatrix.h"
 #include "SkNx.h"
 #include "SkPM4f.h"
 #include "SkShader.h"
 #include "SkTArray.h"
 
 class SkGradientShaderBase::
 GradientShaderBase4fContext : public SkShader::Context {
 public:
     GradientShaderBase4fContext(const SkGradientShaderBase&,
                                 const ContextRec&);
 
     uint32_t getFlags() const override { return fFlags; }
 
+    void shadeSpan(int x, int y, SkPMColor dst[], int count) override;
+    void shadeSpan4f(int x, int y, SkPM4f dst[], int count) override;
+
 protected:
     struct Interval {
         Interval(SkPMColor c0, SkScalar p0,
                  SkPMColor c1, SkScalar p1,
                  const Sk4f& componentScale);
 
         bool isZeroRamp() const { return fZeroRamp; }
 
-        // true when fx is in [p0,p1)
-        bool contains(SkScalar fx) const;
-
         SkPM4f   fC0, fDc;
         SkScalar fP0, fP1;
         bool     fZeroRamp;
     };
 
+    virtual void mapTs(int x, int y, SkScalar ts[], int count) const = 0;
+
+    void buildIntervals(const SkGradientShaderBase&, const ContextRec&, bool reverse);
+
     SkSTArray<8, Interval, true> fIntervals;
     SkMatrix                     fDstToPos;
     SkMatrix::MapXYProc          fDstToPosProc;
     uint8_t                      fDstToPosClass;
     uint8_t                      fFlags;
     bool                         fDither;
     bool                         fColorsArePremul;
 
 private:
     using INHERITED = SkShader::Context;
+
+    void addMirrorIntervals(const SkGradientShaderBase&,
+                            const Sk4f& componentScale, bool reverse);
+
+    template<typename DstType, SkShader::TileMode tileMode>
+    class TSampler;
+
+    template <typename DstType, bool do_premul>
+    void shadePremulSpan(int x, int y, DstType[], int count) const;
+
+    template <typename DstType, bool do_premul, SkShader::TileMode tileMode>
+    void shadeSpanInternal(int x, int y, DstType[], int count) const;
 };
 
 #endif // Sk4fGradientBase_DEFINED