1 files changed, 42 insertions, 0 deletions
diff --git a/src/mbgl/style/data_driven_property_evaluator.hpp b/src/mbgl/style/data_driven_property_evaluator.hpp
new file mode 100644
index 0000000000..7a0ff9a094
--- /dev/null
+++ b/src/mbgl/style/data_driven_property_evaluator.hpp
@@ -0,0 +1,42 @@
+#pragma once
+
+#include <mbgl/style/property_value.hpp>
+#include <mbgl/style/property_evaluation_parameters.hpp>
+#include <mbgl/style/possibly_evaluated_property_value.hpp>
+
+namespace mbgl {
+namespace style {
+
+template <typename T>
+class DataDrivenPropertyEvaluator {
+public:
+    using ResultType = PossiblyEvaluatedPropertyValue<T>;
+
+    DataDrivenPropertyEvaluator(const PropertyEvaluationParameters& parameters_, T defaultValue_)
+        : parameters(parameters_),
+          defaultValue(std::move(defaultValue_)) {}
+
+    ResultType operator()(const Undefined&) const {
+        return ResultType(defaultValue);
+    }
+
+    ResultType operator()(const T& constant) const {
+        return ResultType(constant);
+    }
+
+    ResultType operator()(const CameraFunction<T>& function) const {
+        return ResultType(function.evaluate(parameters.z));
+    }
+
+    template <class Function>
+    ResultType operator()(const Function& function) const {
+        return ResultType(function);
+    }
+
+private:
+    const PropertyEvaluationParameters& parameters;
+    T defaultValue;
+};
+
+} // namespace style
+} // namespace mbgl