[core] property function statistics collection

src/mbgl/style/paint_property_binder.hpp

@@ -4,6 +4,7 @@
 #include <mbgl/gl/attribute.hpp>
 #include <mbgl/gl/uniform.hpp>
 #include <mbgl/util/type_list.hpp>
+#include <mbgl/style/paint_property_statistics.hpp>
 
 namespace mbgl {
 namespace style {
@@ -90,6 +91,8 @@ public:
     virtual float interpolationFactor(float currentZoom) const = 0;
 
     static std::unique_ptr<PaintPropertyBinder> create(const PossiblyEvaluatedPropertyValue<T>& value, float zoom, T defaultValue);
+
+    PaintPropertyStatistics<T> statistics;
 };
 
 template <class T, class A>
@@ -136,7 +139,9 @@ public:
     }
 
     void populateVertexVector(const GeometryTileFeature& feature, std::size_t length) override {
-        auto value = attributeValue(function.evaluate(feature, defaultValue));
+        auto evaluated = function.evaluate(feature, defaultValue);
+        this->statistics.add(evaluated);
+        auto value = attributeValue(evaluated);
         for (std::size_t i = vertexVector.vertexSize(); i < length; ++i) {
             vertexVector.emplace_back(BaseVertex { value });
         }
@@ -187,6 +192,8 @@ public:
 
     void populateVertexVector(const GeometryTileFeature& feature, std::size_t length) override {
         Range<T> range = function.evaluate(std::get<1>(coveringRanges), feature, defaultValue);
+        this->statistics.add(range.min);
+        this->statistics.add(range.max);
         AttributeValue value = zoomInterpolatedAttributeValue(
             attributeValue(range.min),
             attributeValue(range.max));
@@ -312,6 +319,11 @@ public:
         };
     }
 
+    template <class P>
+    const auto& statistics() const {
+        return binders.template get<P>()->statistics;
+    }
+
 private:
     Binders binders;
 };

src/mbgl/style/paint_property_statistics.hpp

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <mbgl/util/optional.hpp>
+
+namespace mbgl {
+namespace style {
+
+template <class T>
+class PaintPropertyStatistics {
+public:
+    optional<T> max() const { return {}; }
+    void add(const T&) {}
+};
+
+template <>
+class PaintPropertyStatistics<float> {
+public:
+    optional<float> max() const {
+        return _max;
+    }
+
+    void add(float value) {
+        _max = _max ? std::max(*_max, value) : value;
+    }
+
+private:
+    optional<float> _max;
+};
+
+} // namespace style
+} // namespace mbgl