1 files changed, 40 insertions, 0 deletions
diff --git a/src/mbgl/renderer/data_driven_property_evaluator.hpp b/src/mbgl/renderer/data_driven_property_evaluator.hpp
index f9452cc572..d65ac36713 100644
--- a/src/mbgl/renderer/data_driven_property_evaluator.hpp
+++ b/src/mbgl/renderer/data_driven_property_evaluator.hpp
@@ -3,6 +3,7 @@
 #include <mbgl/style/property_value.hpp>
 #include <mbgl/renderer/property_evaluation_parameters.hpp>
 #include <mbgl/renderer/possibly_evaluated_property_value.hpp>
+#include <mbgl/renderer/cross_faded_property_evaluator.hpp>
 
 namespace mbgl {
 
@@ -40,4 +41,43 @@ private:
     T defaultValue;
 };
 
+template <typename T>
+class DataDrivenPropertyEvaluator<Faded<T>> {
+public:
+    using ResultType = PossiblyEvaluatedPropertyValue<Faded<T>>;
+
+    DataDrivenPropertyEvaluator(const PropertyEvaluationParameters& parameters_, T defaultValue_)
+    : parameters(parameters_),
+      defaultValue(std::move(defaultValue_)) {}
+
+    ResultType operator()(const T& constant) const {
+        return ResultType(calculate(constant, constant, constant));
+    }
+
+    ResultType operator()(const style::Undefined& ) const {
+        return ResultType(calculate(defaultValue, defaultValue, defaultValue));
+    }
+
+    ResultType operator()(const style::PropertyExpression<T>& expression) const {
+        if (!expression.isFeatureConstant()) {
+            return ResultType(expression);
+        } else {
+            const T evaluated = expression.evaluate(floor(parameters.z));
+            return ResultType(calculate(evaluated, evaluated, evaluated));
+        }
+    }
+
+
+private:
+    Faded<T> calculate(const T& min, const T& mid, const T& max) const {
+        const float z = parameters.z;
+        return z > parameters.zoomHistory.lastIntegerZoom
+            ? Faded<T> { min, mid }
+            : Faded<T> { max, mid };
+    };
+
+    const PropertyEvaluationParameters& parameters;
+    T defaultValue;
+};
+
 } // namespace mbgl