1 files changed, 45 insertions, 0 deletions
diff --git a/src/mbgl/renderer/cross_faded_property_evaluator.hpp b/src/mbgl/renderer/cross_faded_property_evaluator.hpp
new file mode 100644
index 0000000000..40ecba5d93
--- /dev/null
+++ b/src/mbgl/renderer/cross_faded_property_evaluator.hpp
@@ -0,0 +1,45 @@
+#pragma once
+
+#include <mbgl/style/property_value.hpp>
+#include <mbgl/renderer/property_evaluation_parameters.hpp>
+#include <mbgl/util/interpolate.hpp>
+
+namespace mbgl {
+
+template <typename T>
+class Faded {
+public:
+    T from;
+    T to;
+    float fromScale;
+    float toScale;
+    float t;
+};
+
+template <typename T>
+class CrossFadedPropertyEvaluator {
+public:
+    using ResultType = Faded<T>;
+
+    CrossFadedPropertyEvaluator(const PropertyEvaluationParameters& parameters_, T defaultValue_)
+        : parameters(parameters_),
+          defaultValue(std::move(defaultValue_)) {}
+
+    Faded<T> operator()(const style::Undefined&) const;
+    Faded<T> operator()(const T& constant) const;
+    Faded<T> operator()(const style::CameraFunction<T>&) const;
+
+private:
+    Faded<T> calculate(const T& min, const T& mid, const T& max) const;
+
+    const PropertyEvaluationParameters& parameters;
+    T defaultValue;
+};
+
+namespace util {
+template <typename T>
+struct Interpolator<Faded<T>>
+    : Uninterpolated {};
+} // namespace util
+
+} // namespace mbgl