Initial linear gradient 4f impl

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
new file mode 100644
index 0000000000000000000000000000000000000000..7870bc3ccf3a550809ccc54c336bb673593e2274
--- /dev/null
+++ b/src/effects/gradients/Sk4fGradientBase.h
@@ -0,0 +1,61 @@
+/*
+ * 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; }
+
+protected:
+    struct Interval {
+        Interval(SkPMColor c0, SkScalar p0,
+                 SkPMColor c1, SkScalar p1,
+                 const Sk4f& componentScale);
+        Interval(const Sk4f& c0, const Sk4f& dc,
+                 SkScalar p0, SkScalar p1);
+
+        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;
+    };
+
+    const Interval* findInterval(SkScalar fx) const;
+
+    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;
+
+    mutable const Interval*      fCachedInterval;
+};
+
+#endif // Sk4fGradientBase_DEFINED