Initial SVG model

experimental/svg/model/SkSVGValue.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 SkSVGValue_DEFINED
+#define SkSVGValue_DEFINED
+
+#include "SkColor.h"
+#include "SkMatrix.h"
+#include "SkPath.h"
+#include "SkTypes.h"
+
+class SkSVGValue : public SkNoncopyable {
+public:
+    enum class Type {
+        Color,
+        Path,
+        Transform,
+    };
+
+    Type type() const { return fType; }
+
+    template <typename T>
+    const T* as() const {
+        return fType == T::TYPE ? static_cast<const T*>(this) : nullptr;
+    }
+
+protected:
+    SkSVGValue(Type t) : fType(t) { }
+
+private:
+    Type fType;
+};
+
+template <typename SkiaType, SkSVGValue::Type ValueType>
+class SkSVGWrapperValue final : public SkSVGValue {
+public:
+    static constexpr Type TYPE = ValueType;
+
+    explicit SkSVGWrapperValue(const SkiaType& v)
+        : INHERITED(ValueType)
+        , fWrappedValue(v) { }
+
+    operator const SkiaType&() const { return fWrappedValue; }
+
+private:
+    SkiaType fWrappedValue;
+
+    using INHERITED = SkSVGValue;
+};
+
+using SkSVGColorValue     = SkSVGWrapperValue<SkColor , SkSVGValue::Type::Color    >;
+using SkSVGPathValue      = SkSVGWrapperValue<SkPath  , SkSVGValue::Type::Path     >;
+using SkSVGTransformValue = SkSVGWrapperValue<SkMatrix, SkSVGValue::Type::Transform>;
+
+#endif // SkSVGValue_DEFINED