5 files changed, 31 insertions, 24 deletions
diff --git a/include/mbgl/style/function/camera_function.hpp b/include/mbgl/style/function/camera_function.hpp
index 2e4aac2238..7fde365b3d 100644
--- a/include/mbgl/style/function/camera_function.hpp
+++ b/include/mbgl/style/function/camera_function.hpp
@@ -12,7 +12,7 @@ template <class T>
 class CameraFunction {
 public:
     using Stops = std::conditional_t<
-        util::Interpolatable<T>,
+        util::Interpolatable<T>::value,
         variant<
             ExponentialStops<T>,
             IntervalStops<T>>,
@@ -25,7 +25,7 @@ public:
 
     T evaluate(float zoom) const {
         return stops.match([&] (const auto& s) {
-            return s.evaluate(Value(double(zoom))).value_or(T());
+            return s.evaluate(zoom).value_or(T());
         });
     }
     
@@ -35,6 +35,7 @@ public:
     }
 
     Stops stops;
+    bool useIntegerZoom = false;
 };
 
 } // namespace style
diff --git a/include/mbgl/style/function/composite_function.hpp b/include/mbgl/style/function/composite_function.hpp
index b82e63bc37..7b524b6021 100644
--- a/include/mbgl/style/function/composite_function.hpp
+++ b/include/mbgl/style/function/composite_function.hpp
@@ -24,7 +24,7 @@ template <class T>
 class CompositeFunction {
 public:
     using InnerStops = std::conditional_t<
-        util::Interpolatable<T>,
+        util::Interpolatable<T>::value,
         variant<
             ExponentialStops<T>,
             IntervalStops<T>,
@@ -34,7 +34,7 @@ public:
             CategoricalStops<T>>>;
 
     using Stops = std::conditional_t<
-        util::Interpolatable<T>,
+        util::Interpolatable<T>::value,
         variant<
             CompositeExponentialStops<T>,
             CompositeIntervalStops<T>,
@@ -67,7 +67,7 @@ public:
                 
                 // lower_bound yields first element >= zoom, but we want the *last*
                 // element <= zoom, so if we found a stop > zoom, back up by one.
-                if (minIt != s.stops.begin() && minIt->first > zoom) {
+                if (minIt != s.stops.begin() && minIt != s.stops.end() && minIt->first > zoom) {
                     minIt--;
                 }
                 
@@ -135,6 +135,7 @@ public:
     std::string property;
     Stops stops;
     optional<T> defaultValue;
+    bool useIntegerZoom = false;
 
 private:
     T evaluateFinal(const CoveringRanges& ranges, const Value& value, T finalDefaultValue) const {
diff --git a/include/mbgl/style/function/exponential_stops.hpp b/include/mbgl/style/function/exponential_stops.hpp
index 051f5aa9aa..b3866c4059 100644
--- a/include/mbgl/style/function/exponential_stops.hpp
+++ b/include/mbgl/style/function/exponential_stops.hpp
@@ -22,26 +22,28 @@ public:
           base(base_) {
     }
 
-    optional<T> evaluate(const Value& value) const {
+    optional<T> evaluate(float z) const {
         if (stops.empty()) {
-            assert(false);
-            return T();
-        }
-
-        optional<float> z = numericValue<float>(value);
-        if (!z) {
-            return T();
+            return {};
         }
 
-        auto it = stops.upper_bound(*z);
+        auto it = stops.upper_bound(z);
         if (it == stops.end()) {
             return stops.rbegin()->second;
         } else if (it == stops.begin()) {
             return stops.begin()->second;
         } else {
             return util::interpolate(std::prev(it)->second, it->second,
-                util::interpolationFactor(base, { std::prev(it)->first, it->first }, *z));
+                util::interpolationFactor(base, { std::prev(it)->first, it->first }, z));
+        }
+    }
+
+    optional<T> evaluate(const Value& value) const {
+        optional<float> z = numericValue<float>(value);
+        if (!z) {
+            return {};
         }
+        return evaluate(*z);
     }
 
     friend bool operator==(const ExponentialStops& lhs,
diff --git a/include/mbgl/style/function/interval_stops.hpp b/include/mbgl/style/function/interval_stops.hpp
index 50f2b48453..45e2dc6f2e 100644
--- a/include/mbgl/style/function/interval_stops.hpp
+++ b/include/mbgl/style/function/interval_stops.hpp
@@ -18,18 +18,12 @@ public:
         : stops(std::move(stops_)) {
     }
 
-    optional<T> evaluate(const Value& value) const {
+    optional<T> evaluate(float z) const {
         if (stops.empty()) {
-            assert(false);
             return {};
         }
 
-        optional<float> z = numericValue<float>(value);
-        if (!z) {
-            return {};
-        }
-
-        auto it = stops.upper_bound(*z);
+        auto it = stops.upper_bound(z);
         if (it == stops.end()) {
             return stops.rbegin()->second;
         } else if (it == stops.begin()) {
@@ -39,6 +33,14 @@ public:
         }
     }
 
+    optional<T> evaluate(const Value& value) const {
+        optional<float> z = numericValue<float>(value);
+        if (!z) {
+            return {};
+        }
+        return evaluate(*z);
+    }
+
     friend bool operator==(const IntervalStops& lhs,
                            const IntervalStops& rhs) {
         return lhs.stops == rhs.stops;
diff --git a/include/mbgl/style/function/source_function.hpp b/include/mbgl/style/function/source_function.hpp
index f6601d9ea3..9c2ad101ec 100644
--- a/include/mbgl/style/function/source_function.hpp
+++ b/include/mbgl/style/function/source_function.hpp
@@ -16,7 +16,7 @@ template <class T>
 class SourceFunction {
 public:
     using Stops = std::conditional_t<
-        util::Interpolatable<T>,
+        util::Interpolatable<T>::value,
         variant<
             ExponentialStops<T>,
             IntervalStops<T>,
@@ -53,6 +53,7 @@ public:
     std::string property;
     Stops stops;
     optional<T> defaultValue;
+    bool useIntegerZoom = false;
 };
 
 } // namespace style