Generic 4f gradient T sampler fallback

src/effects/gradients/Sk4fGradientBase.h

Index: src/effects/gradients/Sk4fGradientBase.h
diff --git a/src/effects/gradients/Sk4fGradientBase.h b/src/effects/gradients/Sk4fGradientBase.h
index 1fece72b520fd327c3607bb24218cd4b3178aaec..706e0b7b185e75b173b68ccb5df28088ab92ae2c 100644
--- a/src/effects/gradients/Sk4fGradientBase.h
+++ b/src/effects/gradients/Sk4fGradientBase.h
@@ -24,6 +24,9 @@ public:
 
     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,
@@ -32,14 +35,15 @@ protected:
 
         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;
@@ -50,6 +54,18 @@ protected:
 
 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 premul>

[reed1, 2016/03/10 17:49:37]

does this mean you will apply alpha to the colors as part of your processing, or
that your inputs have already had that done, and you will do nothing in your
processing?

[f(malita), 2016/03/10 18:46:10]

The former: interval colors are in unpremul format, so we have to apply alpha as
part of processing.  Renamed to 'do_premul' to hopefully clarify.

+    void shadePremulSpan(int x, int y, DstType[], int count) const;
+
+    template <typename DstType, bool premul, SkShader::TileMode tileMode>
+    void shadeSpanInternal(int x, int y, DstType[], int count) const;
 };
 
 #endif // Sk4fGradientBase_DEFINED