refactor functions

14 files changed, 605 insertions, 386 deletions

diff --git a/bin/style.js b/bin/style.js
index 7ca40b6123..691c913510 100644
--- a/bin/style.js
+++ b/bin/style.js
@@ -6,7 +6,7 @@ module.exports = {
     "@land": "#eee",
     "@water": "#999",
     "@park": "#bda",
-    "@road": "#fefefe",
+    "@road": "#FF00FF",
     "@border": "#6d90ab",
     "@building": "#ddd",
     "@building_outline": "#ccc",
@@ -53,28 +53,26 @@ module.exports = {
       "fill-color": "blue"
     }
   }, {
-    "id": "roads",
-    "layers": [{
-      "id": "road",
-      "source": "mapbox.mapbox-streets-v5",
-      "source-layer": "road",
-      "render": {
-        "type": "line",
-        "line-cap": "round",
-        "line-join": "bevel"
-      },
-      "style": {
-        "line-color": "@road",
-        "line-blur": "@road_blur",
-        "line-width": {
-          "fn": "exponential",
-          "z": 10,
-          "val": -1,
-          "slope": 0.2,
-          "min": 1
-        }
+    "id": "road",
+    "source": "mapbox.mapbox-streets-v5",
+    "source-layer": "road",
+    "render": {
+      "type": "line",
+      "line-cap": "round",
+      "line-join": "bevel"
+    },
+    "style": {
+      "line-color": "@road",
+      "line-blur": "@road_blur",
+      "line-width": {
+        "fn": "exponential",
+        "z": 10,
+        "val": -1,
+        "slope": 0.2,
+        "min": 1,
+        "max": 1000
       }
-    }]
+    }
   }, {
     "id": "building",
     "source": "mapbox.mapbox-streets-v5",
diff --git a/include/llmr/style/function_properties.hpp b/include/llmr/style/function_properties.hpp
index 970d617d02..d1e1a5b1c6 100644
--- a/include/llmr/style/function_properties.hpp
+++ b/include/llmr/style/function_properties.hpp
@@ -1,43 +1,72 @@
 #ifndef LLMR_STYLE_FUNCTION_PROPERTIES
 #define LLMR_STYLE_FUNCTION_PROPERTIES
 
+#include <llmr/util/variant.hpp>
+
 #include <vector>
 
 namespace llmr {
 
-namespace functions {
+template <typename T>
+struct ConstantFunction {
+    inline ConstantFunction(const T &value) : value(value) {}
+    inline T evaluate(float) const { return value; }
 
-float null(float z, const std::vector<float>&);
-float constant(float z, const std::vector<float>& values);
-float min(float z, const std::vector<float>& values);
-float max(float z, const std::vector<float>& values);
-float stops(float z, const std::vector<float>& values);
-float linear(float z, const std::vector<float>& values);
-float exponential(float z, const std::vector<float>& values);
+private:
+    const T value;
+};
 
-}
+template <typename T>
+struct LinearFunction {
+    inline LinearFunction(const T &value, float z_base, float slope, const T &min, const T &max)
+        : value(value), min(min), max(max), z_base(z_base), slope(slope) {}
+    T evaluate(float z) const;
 
-struct FunctionProperty {
-    typedef float (*fn)(float z, const std::vector<float>& values);
+private:
+    const T value, min, max;
+    const float z_base, slope;
+};
 
-    fn function;
-    std::vector<float> values;
+template <typename T>
+struct ExponentialFunction {
+    inline ExponentialFunction(const T &value, float z_base, float slope, const T &min,
+                               const T &max)
+        : value(value), min(min), max(max), z_base(z_base), slope(slope) {}
+    T evaluate(float z) const;
 
-    inline FunctionProperty() : function(&functions::null) {}
+private:
+    const T value, min, max;
+    const float z_base, slope;
+};
 
-    inline FunctionProperty(const FunctionProperty &property)
-        : function(property.function), values(property.values) {}
-    inline FunctionProperty(FunctionProperty &&property)
-        : function(property.function), values(std::move(property.values)) {}
+template <typename T>
+struct StopsFunction {
+    inline StopsFunction(const std::vector<std::pair<float, T>> &values) : values(values) {}
+    T evaluate(float z) const;
 
+private:
+    const std::vector<std::pair<float, T>> values;
+};
 
-    inline void operator=(const FunctionProperty &rhs) {
-        function = rhs.function;
-        values = rhs.values;
-    }
+template <typename T>
+using Function = util::variant<
+    ConstantFunction<T>,
+    LinearFunction<T>,
+    ExponentialFunction<T>,
+    StopsFunction<T>
+>;
 
-    inline FunctionProperty(float value) : function(&functions::constant), values(1, value) {}
-    template <typename T> inline T evaluate(float z) const { return function(z, values); }
+template <typename T>
+struct FunctionEvaluator {
+    typedef T result_type;
+    inline FunctionEvaluator(float z) : z(z) {}
+
+    template <template <typename> class Fn>
+    inline result_type operator()(const Fn<T>& fn) {
+        return fn.evaluate(z);
+    }
+private:
+    float z;
 };
 
 }
diff --git a/include/llmr/style/property_value.hpp b/include/llmr/style/property_value.hpp
index 9772258da8..f648e9bef6 100644
--- a/include/llmr/style/property_value.hpp
+++ b/include/llmr/style/property_value.hpp
@@ -8,12 +8,15 @@
 namespace llmr {
 
 typedef util::variant<
-    FunctionProperty,
-    TranslateAnchorType,
-    RotateAnchorType,
+    bool,
+    float,
     Color,
     std::string,
-    bool
+    TranslateAnchorType,
+    RotateAnchorType,
+    Function<bool>,
+    Function<float>,
+    Function<Color>
 > PropertyValue;
 
 }
diff --git a/include/llmr/style/rasterize_properties.hpp b/include/llmr/style/rasterize_properties.hpp
index f085a7bdd9..2e1fc32895 100644
--- a/include/llmr/style/rasterize_properties.hpp
+++ b/include/llmr/style/rasterize_properties.hpp
@@ -15,10 +15,10 @@ struct PrerenderProperties {
 
 class RasterizeProperties {
 public:
-    boost::optional<FunctionProperty> enabled;
-    boost::optional<FunctionProperty> buffer;
-    boost::optional<FunctionProperty> size;
-    boost::optional<FunctionProperty> blur;
+    boost::optional<Function<bool>> enabled;
+    boost::optional<Function<float>> buffer;
+    boost::optional<Function<float>> size;
+    boost::optional<Function<float>> blur;
 };
 
 }
diff --git a/include/llmr/style/style.hpp b/include/llmr/style/style.hpp
index 62864b75ff..6b9b4549cc 100644
--- a/include/llmr/style/style.hpp
+++ b/include/llmr/style/style.hpp
@@ -39,6 +39,10 @@ public:
     const std::vector<std::string> &getAppliedClasses() const;
     void toggleClass(const std::string &name);
 
+    // Updates the styling information to reflect the current array
+    // of applied classes.
+    void updateClasses();
+
 public:
     std::shared_ptr<Sprite> sprite;
     std::shared_ptr<StyleLayerGroup> layers;
@@ -49,9 +53,6 @@ private:
     void updateSources();
     void updateSources(const std::shared_ptr<StyleLayerGroup> &group);
 
-    void updateProperties(const std::shared_ptr<StyleLayerGroup> &group, float z, timestamp t);
-
-    void updateClasses();
 
 private:
     std::set<std::shared_ptr<Source>> activeSources;
diff --git a/include/llmr/style/style_layer.hpp b/include/llmr/style/style_layer.hpp
index 89d4e14764..b04970f7c1 100644
--- a/include/llmr/style/style_layer.hpp
+++ b/include/llmr/style/style_layer.hpp
@@ -24,8 +24,8 @@ public:
         std::unique_ptr<const RasterizeProperties> &&rasterize);
 
     template <typename T> const T &getProperties() {
-        if (style.is<T>()) {
-            return style.get<T>();
+        if (properties.is<T>()) {
+            return properties.get<T>();
         } else {
             return defaultStyleProperties<T>();
         }
@@ -36,7 +36,7 @@ public:
 
     // Updates the StyleProperties information in this layer by evaluating all
     // pending transitions and applied classes in order.
-    void updateStyle(float z);
+    void updateProperties(float z, timestamp t);
 
     // Sets the list of classes and creates transitions to the currently applied values.
     void setClasses(const std::vector<std::string> &class_names, timestamp now,
@@ -47,6 +47,11 @@ private:
     void applyClassProperties(ClassID class_id, std::set<PropertyKey> &already_applied,
                               timestamp now, const PropertyTransition &defaultTransition);
 
+    // Sets the properties of this object by evaluating all pending transitions and
+    // aplied classes in order.
+    template <typename T> void applyStyleProperties(float z, timestamp t);
+    template <typename T> void applyStyleProperty(PropertyKey key, T &, float z, timestamp t);
+
 public:
     // The name of this layer.
     const std::string id;
@@ -66,7 +71,7 @@ private:
 public:
     // Stores the evaluated, and cascaded styling information, specific to this
     // layer's type.
-    StyleProperties style;
+    StyleProperties properties;
 
     // Rasterization properties are used for prerendering the tile to a bitmap,
     // which is then used as a raster image instead of rendering this layer
diff --git a/include/llmr/style/style_layer_group.hpp b/include/llmr/style/style_layer_group.hpp
index 73214830fe..2122c16286 100644
--- a/include/llmr/style/style_layer_group.hpp
+++ b/include/llmr/style/style_layer_group.hpp
@@ -11,6 +11,7 @@ class StyleLayerGroup {
 public:
     void setClasses(const std::vector<std::string> &class_names, timestamp now,
                     const PropertyTransition &defaultTransition);
+    void updateProperties(float z, timestamp t);
 
 public:
     std::vector<std::shared_ptr<StyleLayer>> layers;
diff --git a/include/llmr/style/style_parser.hpp b/include/llmr/style/style_parser.hpp
index 3c2a12a2a3..abf047fc17 100644
--- a/include/llmr/style/style_parser.hpp
+++ b/include/llmr/style/style_parser.hpp
@@ -59,6 +59,11 @@ private:
     template <typename T>
     bool parseStyleProperty(const char *property_name, const std::vector<PropertyKey> &keys, ClassProperties &klass, JSVal value);
 
+    template <typename T>
+    bool parseFunction(PropertyKey key, ClassProperties &klass, JSVal value);
+    template <typename T>
+    T parseFunctionArgument(JSVal value);
+
 
     FilterExpression parseFilter(JSVal, FilterExpression::Operator op);
     FilterExpression parseFilter(JSVal);
diff --git a/src/style/function_properties.cpp b/src/style/function_properties.cpp
index eaaa2ad6fe..98f6503be3 100644
--- a/src/style/function_properties.cpp
+++ b/src/style/function_properties.cpp
@@ -1,86 +1,131 @@
 #include <llmr/style/function_properties.hpp>
+#include <llmr/style/types.hpp>
 
 #include <cmath>
 
 namespace llmr {
 
-float functions::null(float, const std::vector<float>&) {
-    return 0;
+
+template <>
+bool LinearFunction<bool>::evaluate(float z) const {
+    return z < z_base ? slope >= 0 : z > z_base ? slope >= 0 : value;
+}
+
+template <>
+float LinearFunction<float>::evaluate(float z) const {
+    return std::fmin(std::fmax(min, value + (z - z_base) * slope), max);
 }
 
-float functions::constant(float, const std::vector<float>& values) {
-    return values.size() >= 1 ? values.front() : 0.0f;
+template <>
+Color LinearFunction<Color>::evaluate(float z) const {
+    return {{
+        std::fmin(std::fmax(min[0], value[0] + (z - z_base) * slope), max[0]),
+        std::fmin(std::fmax(min[1], value[1] + (z - z_base) * slope), max[1]),
+        std::fmin(std::fmax(min[2], value[2] + (z - z_base) * slope), max[2]),
+        std::fmin(std::fmax(min[3], value[3] + (z - z_base) * slope), max[3])
+    }};
+}
+
+
+template <>
+bool ExponentialFunction<bool>::evaluate(float z) const {
+    return z < z_base ? slope >= 0 : z > z_base ? slope >= 0 : value;
+}
+
+template <>
+float ExponentialFunction<float>::evaluate(float z) const {
+    return std::fmin(std::fmax(min, value + std::pow(1.75, (z - z_base)) * slope), max);
+}
+
+template <>
+Color ExponentialFunction<Color>::evaluate(float z) const {
+    return {{
+        std::fmin(std::fmax(min[0], value[0] + float(std::pow(1.75, (z - z_base))) * slope), max[0]),
+        std::fmin(std::fmax(min[1], value[1] + float(std::pow(1.75, (z - z_base))) * slope), max[1]),
+        std::fmin(std::fmax(min[2], value[2] + float(std::pow(1.75, (z - z_base))) * slope), max[2]),
+        std::fmin(std::fmax(min[3], value[3] + float(std::pow(1.75, (z - z_base))) * slope), max[3])
+    }};
+}
+
+template <typename T>
+inline T exponentialInterpolate(T smaller, T larger, const float factor);
+
+template <>
+inline float exponentialInterpolate(const float smaller, const float larger, const float factor) {
+    // Linear interpolation if base is 0
+    if (smaller == 0.0f) {
+        return factor * larger;
+    }
+    // Exponential interpolation between the values
+    return smaller * std::pow(larger / smaller, factor);
 }
 
-float functions::min(float z, const std::vector<float>& values) {
-    return values.size() >= 1 && z >= values.front();
+template <>
+inline bool exponentialInterpolate(const bool smaller, const bool larger, const float factor) {
+    return exponentialInterpolate(float(smaller), float(larger), factor);
 }
 
-float functions::max(float z, const std::vector<float>& values) {
-    return values.size() >= 1 && z <= values.front();
+template <>
+inline Color exponentialInterpolate(const Color smaller, const Color larger, const float factor) {
+    return {{
+        exponentialInterpolate(smaller[0], larger[0], factor),
+        exponentialInterpolate(smaller[1], larger[1], factor),
+        exponentialInterpolate(smaller[2], larger[2], factor),
+        exponentialInterpolate(smaller[3], larger[3], factor)
+    }};
 }
 
-float functions::stops(float z, const std::vector<float>& stops) {
-    // We need an even number of stop values.
-    if (stops.size() % 2 != 0) return 0;
 
+template <typename T>
+T exponentialDefault();
+
+template <> bool exponentialDefault() { return true; }
+template <> float exponentialDefault() { return 1.0f; }
+template <> Color exponentialDefault() { return {{ 0, 0, 0, 1 }}; }
+
+
+template <typename T>
+T StopsFunction<T>::evaluate(float z) const {
     bool smaller = false;
-    float smaller_z = 0.0;
-    float smaller_val = 0.0;
+    float smaller_z = 0.0f;
+    T smaller_val {};
     bool larger = false;
-    float larger_z = 0.0;
-    float larger_val = 0.0;
-
-    for (uint32_t i = 0; i < stops.size(); i += 2) {
-        float stop_z = stops[i];
-        float stop_val = stops[i + 1];
-        if (stop_z <= z && (!smaller || smaller_z < stop_z)) { smaller = true; smaller_z = stop_z; smaller_val = stop_val; }
-        if (stop_z >= z && (!larger || larger_z > stop_z)) { larger = true; larger_z = stop_z; larger_val = stop_val; }
+    float larger_z = 0.0f;
+    T larger_val {};
+
+    for (uint32_t i = 0; i < values.size(); i++) {
+        float stop_z = values[i].first;
+        T stop_val = values[i].second;
+        if (stop_z <= z && (!smaller || smaller_z < stop_z)) {
+            smaller = true;
+            smaller_z = stop_z;
+            smaller_val = stop_val;
+        }
+        if (stop_z >= z && (!larger || larger_z > stop_z)) {
+            larger = true;
+            larger_z = stop_z;
+            larger_val = stop_val;
+        }
     }
 
     if (smaller && larger) {
-        if (larger_z == smaller_z || larger_val == smaller_val) return smaller_val;
+        if (larger_z == smaller_z || larger_val == smaller_val) {
+            return smaller_val;
+        }
         float factor = (z - smaller_z) / (larger_z - smaller_z);
-        // Linear interpolation if base is 0
-        if (smaller_val == 0) return factor * larger_val;
-        // Exponential interpolation between the values
-        return smaller_val * std::pow(larger_val / smaller_val, factor);
+        return exponentialInterpolate<T>(smaller_val, larger_val, factor);
     } else if (larger) {
         return larger_val;
     } else if (smaller) {
         return smaller_val;
     } else {
         // No stop defined.
-        return 1;
+        return exponentialDefault<T>();
     }
 }
 
-float functions::linear(float z, const std::vector<float>& values) {
-    if (values.size() != 5) {
-        return 0;
-    }
-
-    const float z_base = values[0];
-    const float val = values[1];
-    const float slope = values[2];
-    const float min = values[3];
-    const float max = values[4];
-
-    return std::fmin(std::fmax(min, val + (z - z_base) * slope), max);
-}
-
-float functions::exponential(float z, const std::vector<float>& values) {
-    if (values.size() != 5) {
-        return 0;
-    }
-
-    const float z_base = values[0];
-    const float val = values[1];
-    const float slope = values[2];
-    const float min = values[3];
-    const float max = values[4];
-
-    return std::fmin(std::fmax(min, val + std::pow(1.75, (z - z_base)) * slope), max);
-}
+template bool StopsFunction<bool>::evaluate(float z) const;
+template float StopsFunction<float>::evaluate(float z) const;
+template Color StopsFunction<Color>::evaluate(float z) const;
 
 }
diff --git a/src/style/property_fallback.cpp b/src/style/property_fallback.cpp
index d94f7e9e54..b57a6a216b 100644
--- a/src/style/property_fallback.cpp
+++ b/src/style/property_fallback.cpp
@@ -51,6 +51,6 @@ const std::map<PropertyKey, PropertyValue> PropertyFallbackValue::properties = {
     { PropertyKey::BackgroundColor, Color({{ 0, 0, 0, 0 }}) },
 };
 
-const PropertyValue PropertyFallbackValue::defaultProperty;
+const PropertyValue PropertyFallbackValue::defaultProperty = PropertyValue();
 
 }
diff --git a/src/style/style.cpp b/src/style/style.cpp
index c2794fed88..a08e77ac01 100644
--- a/src/style/style.cpp
+++ b/src/style/style.cpp
@@ -38,154 +38,14 @@ void Style::updateSources(const std::shared_ptr<StyleLayerGroup> &group) {
     }
 }
 
-StyleProperties resetClassProperties(StyleLayer &layer) {
-    if (layer.layers) {
-        return CompositeProperties();
-    } else if (layer.bucket) {
-        switch (layer.bucket->type) {
-            case BucketType::Fill: return FillProperties(); break;
-            case BucketType::Line: return LineProperties(); break;
-            case BucketType::Icon: return IconProperties(); break;
-            case BucketType::Text: return TextProperties(); break;
-            case BucketType::Raster: return RasterProperties(); break;
-            default: return std::false_type(); break;
-        }
-    } else {
-        return BackgroundProperties();
-    }
-}
-
-template <typename T>
-void applyProperty(const ClassProperties &properties, PropertyKey key, T &target) {
-    auto it = properties.properties.find(key);
-    if (it != properties.properties.end()) {
-        const PropertyValue &value = it->second;
-        if (value.is<T>()) {
-            target = value.get<T>();
-        }
-    }
-}
-
-template <typename T>
-void applyProperty(const ClassProperties &properties, PropertyKey key, T &target, float z) {
-    auto it = properties.properties.find(key);
-    if (it != properties.properties.end()) {
-        const PropertyValue &value = it->second;
-        if (value.is<FunctionProperty>()) {
-            target = value.get<FunctionProperty>().evaluate<T>(z);
-        } else if (value.is<bool>()) {
-            target = value.get<bool>();
-        }
-    }
-}
-
-void applyClassProperties(StyleProperties &style, const ClassProperties &properties, float z) {
-    if (style.is<FillProperties>()) {
-        FillProperties &fill = style.get<FillProperties>();
-        applyProperty(properties, PropertyKey::FillEnabled, fill.enabled, z);
-        applyProperty(properties, PropertyKey::FillAntialias, fill.antialias, z);
-        applyProperty(properties, PropertyKey::FillOpacity, fill.opacity, z);
-        applyProperty(properties, PropertyKey::FillColor, fill.fill_color);
-        applyProperty(properties, PropertyKey::FillOutlineColor, fill.stroke_color);
-        applyProperty(properties, PropertyKey::FillTranslateX, fill.translate[0], z);
-        applyProperty(properties, PropertyKey::FillTranslateY, fill.translate[1], z);
-        applyProperty(properties, PropertyKey::FillTranslateAnchor, fill.translateAnchor);
-        applyProperty(properties, PropertyKey::FillImage, fill.image);
-    } else if (style.is<LineProperties>()) {
-        LineProperties &line = style.get<LineProperties>();
-        applyProperty(properties, PropertyKey::LineEnabled, line.enabled, z);
-        applyProperty(properties, PropertyKey::LineOpacity, line.opacity, z);
-        applyProperty(properties, PropertyKey::LineColor, line.color);
-        applyProperty(properties, PropertyKey::LineTranslateX, line.translate[0], z);
-        applyProperty(properties, PropertyKey::LineTranslateY, line.translate[1], z);
-        applyProperty(properties, PropertyKey::LineTranslateAnchor, line.translateAnchor);
-        applyProperty(properties, PropertyKey::LineWidth, line.width, z);
-        applyProperty(properties, PropertyKey::LineOffset, line.offset, z);
-        applyProperty(properties, PropertyKey::LineBlur, line.blur, z);
-        applyProperty(properties, PropertyKey::LineDashLand, line.dash_array[0], z);
-        applyProperty(properties, PropertyKey::LineDashGap, line.dash_array[1], z);
-        applyProperty(properties, PropertyKey::LineImage, line.image);
-    } else if (style.is<IconProperties>()) {
-        IconProperties &icon = style.get<IconProperties>();
-        applyProperty(properties, PropertyKey::IconEnabled, icon.enabled, z);
-        applyProperty(properties, PropertyKey::IconOpacity, icon.opacity, z);
-        applyProperty(properties, PropertyKey::IconRotate, icon.rotate, z);
-        applyProperty(properties, PropertyKey::IconRotateAnchor, icon.rotate_anchor);
-    } else if (style.is<TextProperties>()) {
-        TextProperties &text = style.get<TextProperties>();
-        applyProperty(properties, PropertyKey::TextEnabled, text.enabled, z);
-        applyProperty(properties, PropertyKey::TextOpacity, text.opacity, z);
-        applyProperty(properties, PropertyKey::TextSize, text.size, z);
-        applyProperty(properties, PropertyKey::TextColor, text.color);
-        applyProperty(properties, PropertyKey::TextHaloColor, text.halo_color);
-        applyProperty(properties, PropertyKey::TextHaloWidth, text.halo_width, z);
-        applyProperty(properties, PropertyKey::TextHaloBlur, text.halo_blur, z);
-    } else if (style.is<CompositeProperties>()) {
-        CompositeProperties &composite = style.get<CompositeProperties>();
-        applyProperty(properties, PropertyKey::CompositeEnabled, composite.enabled, z);
-        applyProperty(properties, PropertyKey::CompositeOpacity, composite.opacity, z);
-    } else if (style.is<RasterProperties>()) {
-        RasterProperties &raster = style.get<RasterProperties>();
-        applyProperty(properties, PropertyKey::RasterEnabled, raster.enabled, z);
-        applyProperty(properties, PropertyKey::RasterOpacity, raster.opacity, z);
-        applyProperty(properties, PropertyKey::RasterSpin, raster.spin, z);
-        applyProperty(properties, PropertyKey::RasterBrightnessLow, raster.brightness[0], z);
-        applyProperty(properties, PropertyKey::RasterBrightnessHigh, raster.brightness[1], z);
-        applyProperty(properties, PropertyKey::RasterSaturation, raster.saturation, z);
-        applyProperty(properties, PropertyKey::RasterContrast, raster.contrast, z);
-        applyProperty(properties, PropertyKey::RasterFade, raster.fade, z);
-    } else if (style.is<BackgroundProperties>()) {
-        BackgroundProperties &background = style.get<BackgroundProperties>();
-        applyProperty(properties, PropertyKey::BackgroundColor, background.color);
-    }
-}
-
-void Style::updateProperties(const std::shared_ptr<StyleLayerGroup> &group, float z, timestamp t) {
-    if (!group) {
-        return;
-    }
-
-    for (const std::shared_ptr<StyleLayer> &layer : group->layers) {
-        if (!layer) continue;
-
-        if (layer->layers) {
-            updateProperties(layer->layers, z, t);
-        }
-
-        // Accomodate for different tile size.
-        if (layer->bucket) {
-            const StyleBucket &bucket = *layer->bucket;
-            if (bucket.source) {
-                const Source &source = *bucket.source;
-                z += std::log(source.tile_size / 256.0f) / M_LN2;
-            }
-        }
-
-        layer->style = resetClassProperties(*layer);
-
-        // Apply default class (if exists)
-        auto default_it = layer->styles.find(ClassID::Default);
-        if (default_it != layer->styles.end()) {
-            applyClassProperties(layer->style, default_it->second, z);
-        }
-
-        // Apply overriding classes in order.
-        for (const std::string &class_name : appliedClasses) {
-            const ClassID class_id = ClassDictionary::Lookup(class_name);
-            auto class_it = layer->styles.find(class_id);
-            if (class_it != layer->styles.end()) {
-                applyClassProperties(layer->style, class_it->second, z);
-            }
-        }
-    }
-}
-
 void Style::updateProperties(float z, timestamp t) {
     uv::writelock lock(mtx);
 
     updateSources();
 
-    updateProperties(layers, z, t);
+    if (layers) {
+        layers->updateProperties(z, t);
+    }
 
     // Apply transitions after the first time.
     if (!initial_render_complete) {
@@ -231,6 +91,8 @@ void Style::loadJSON(const uint8_t *const data) {
     parser.parse(const_cast<const rapidjson::Document &>(doc));
 
     layers = parser.getLayers();
+
+    updateClasses();
 }
 
 }
diff --git a/src/style/style_layer.cpp b/src/style/style_layer.cpp
index 3bfd235796..19497aa9e9 100644
--- a/src/style/style_layer.cpp
+++ b/src/style/style_layer.cpp
@@ -1,4 +1,6 @@
 #include <llmr/style/style_layer.hpp>
+#include <llmr/style/style_bucket.hpp>
+#include <llmr/map/source.hpp>
 #include <llmr/style/style_layer_group.hpp>
 #include <llmr/style/property_fallback.hpp>
 
@@ -94,4 +96,177 @@ void StyleLayer::applyClassProperties(const ClassID class_id,
     }
 }
 
+//void applyStyleProperties(StyleProperties &style, const ClassProperties &properties, float z) {
+//    if (style.is<FillProperties>()) {
+//        FillProperties &fill = style.get<FillProperties>();
+//        applyStyleProperty(properties, PropertyKey::FillEnabled, fill.enabled, z);
+//        applyStyleProperty(properties, PropertyKey::FillAntialias, fill.antialias, z);
+//        applyStyleProperty(properties, PropertyKey::FillOpacity, fill.opacity, z);
+//        applyStyleProperty(properties, PropertyKey::FillColor, fill.fill_color);
+//        applyStyleProperty(properties, PropertyKey::FillOutlineColor, fill.stroke_color);
+//        applyStyleProperty(properties, PropertyKey::FillTranslateX, fill.translate[0], z);
+//        applyStyleProperty(properties, PropertyKey::FillTranslateY, fill.translate[1], z);
+//        applyStyleProperty(properties, PropertyKey::FillTranslateAnchor, fill.translateAnchor);
+//        applyStyleProperty(properties, PropertyKey::FillImage, fill.image);
+//    } else if (style.is<LineProperties>()) {
+//        LineProperties &line = style.get<LineProperties>();
+//        applyStyleProperty(properties, PropertyKey::LineEnabled, line.enabled, z);
+//        applyStyleProperty(properties, PropertyKey::LineOpacity, line.opacity, z);
+//        applyStyleProperty(properties, PropertyKey::LineColor, line.color);
+//        applyStyleProperty(properties, PropertyKey::LineTranslateX, line.translate[0], z);
+//        applyStyleProperty(properties, PropertyKey::LineTranslateY, line.translate[1], z);
+//        applyStyleProperty(properties, PropertyKey::LineTranslateAnchor, line.translateAnchor);
+//        applyStyleProperty(properties, PropertyKey::LineWidth, line.width, z);
+//        applyStyleProperty(properties, PropertyKey::LineOffset, line.offset, z);
+//        applyStyleProperty(properties, PropertyKey::LineBlur, line.blur, z);
+//        applyStyleProperty(properties, PropertyKey::LineDashLand, line.dash_array[0], z);
+//        applyStyleProperty(properties, PropertyKey::LineDashGap, line.dash_array[1], z);
+//        applyStyleProperty(properties, PropertyKey::LineImage, line.image);
+//    } else if (style.is<IconProperties>()) {
+//        IconProperties &icon = style.get<IconProperties>();
+//        applyStyleProperty(properties, PropertyKey::IconEnabled, icon.enabled, z);
+//        applyStyleProperty(properties, PropertyKey::IconOpacity, icon.opacity, z);
+//        applyStyleProperty(properties, PropertyKey::IconRotate, icon.rotate, z);
+//        applyStyleProperty(properties, PropertyKey::IconRotateAnchor, icon.rotate_anchor);
+//    } else if (style.is<TextProperties>()) {
+//        TextProperties &text = style.get<TextProperties>();
+//        applyStyleProperty(properties, PropertyKey::TextEnabled, text.enabled, z);
+//        applyStyleProperty(properties, PropertyKey::TextOpacity, text.opacity, z);
+//        applyStyleProperty(properties, PropertyKey::TextSize, text.size, z);
+//        applyStyleProperty(properties, PropertyKey::TextColor, text.color);
+//        applyStyleProperty(properties, PropertyKey::TextHaloColor, text.halo_color);
+//        applyStyleProperty(properties, PropertyKey::TextHaloWidth, text.halo_width, z);
+//        applyStyleProperty(properties, PropertyKey::TextHaloBlur, text.halo_blur, z);
+//    } else if (style.is<CompositeProperties>()) {
+//        CompositeProperties &composite = style.get<CompositeProperties>();
+//        applyStyleProperty(properties, PropertyKey::CompositeEnabled, composite.enabled, z);
+//        applyStyleProperty(properties, PropertyKey::CompositeOpacity, composite.opacity, z);
+//    } else if (style.is<RasterProperties>()) {
+//        RasterProperties &raster = style.get<RasterProperties>();
+//        applyStyleProperty(properties, PropertyKey::RasterEnabled, raster.enabled, z);
+//        applyStyleProperty(properties, PropertyKey::RasterOpacity, raster.opacity, z);
+//        applyStyleProperty(properties, PropertyKey::RasterSpin, raster.spin, z);
+//        applyStyleProperty(properties, PropertyKey::RasterBrightnessLow, raster.brightness[0], z);
+//        applyStyleProperty(properties, PropertyKey::RasterBrightnessHigh, raster.brightness[1], z);
+//        applyStyleProperty(properties, PropertyKey::RasterSaturation, raster.saturation, z);
+//        applyStyleProperty(properties, PropertyKey::RasterContrast, raster.contrast, z);
+//        applyStyleProperty(properties, PropertyKey::RasterFade, raster.fade, z);
+//    } else if (style.is<BackgroundProperties>()) {
+//        BackgroundProperties &background = style.get<BackgroundProperties>();
+//        applyStyleProperty(properties, PropertyKey::BackgroundColor, background.color);
+//    }
+//}
+//
+
+template <typename T>
+struct PropertyEvaluator {
+    typedef T result_type;
+    PropertyEvaluator(float z) : z(z) {}
+
+    template <typename P, typename std::enable_if<std::is_convertible<P, T>::value, int>::type = 0>
+    T operator()(const P &value) const {
+        return value;
+    }
+
+    T operator()(const Function<T> &value) const {
+        return util::apply_visitor(FunctionEvaluator<T>(z), value);
+    }
+
+    template <typename P, typename std::enable_if<!std::is_convertible<P, T>::value, int>::type = 0>
+    T operator()(const P &) const {
+        return T();
+    }
+
+private:
+    const float z;
+};
+
+template <typename T>
+void StyleLayer::applyStyleProperty(PropertyKey key, T &target, const float z, const timestamp t) {
+    auto it = appliedStyle.find(key);
+    if (it != appliedStyle.end()) {
+        AppliedClassProperties &applied = it->second;
+        // Iterate through all properties that we need to apply in order.
+        const PropertyEvaluator<T> evaluator(z);
+        for (AppliedClassProperty &property : applied.properties) {
+            if (property.end >= t) {
+                // We overwrite the current property with the new value.
+                target = util::apply_visitor(evaluator, property.value);
+            } else if (property.begin <= t) {
+                // We overwrite the current property partially with the new value.
+                float progress = float(t - property.begin) / float(property.end - property.begin);
+                target = util::apply_visitor(evaluator, property.value);
+//                target = (1.0f - progress) * target + (progress) *
+//                evaluateProperty(property.value, target, z);
+            }
+        }
+    }
+}
+
+
+template <typename T>
+void StyleLayer::applyStyleProperties(float, timestamp) {
+    properties.set<std::false_type>();
+}
+
+template <>
+void StyleLayer::applyStyleProperties<FillProperties>(const float z, const timestamp t) {
+    properties.set<FillProperties>();
+    FillProperties &fill = properties.get<FillProperties>();
+    applyStyleProperty(PropertyKey::FillEnabled, fill.enabled, z, t);
+    applyStyleProperty(PropertyKey::FillAntialias, fill.antialias, z, t);
+    applyStyleProperty(PropertyKey::FillOpacity, fill.opacity, z, t);
+    applyStyleProperty(PropertyKey::FillColor, fill.fill_color, z, t);
+    applyStyleProperty(PropertyKey::FillOutlineColor, fill.stroke_color, z, t);
+    applyStyleProperty(PropertyKey::FillTranslateX, fill.translate[0], z, t);
+    applyStyleProperty(PropertyKey::FillTranslateY, fill.translate[1], z, t);
+    applyStyleProperty(PropertyKey::FillTranslateAnchor, fill.translateAnchor, z, t);
+    applyStyleProperty(PropertyKey::FillImage, fill.image, z, t);
+}
+
+template <>
+void StyleLayer::applyStyleProperties<LineProperties>(const float z, const timestamp t) {
+    properties.set<LineProperties>();
+    LineProperties &line = properties.get<LineProperties>();
+    applyStyleProperty(PropertyKey::LineEnabled, line.enabled, z, t);
+    applyStyleProperty(PropertyKey::LineOpacity, line.opacity, z, t);
+    applyStyleProperty(PropertyKey::LineColor, line.color, z, t);
+    applyStyleProperty(PropertyKey::LineTranslateX, line.translate[0], z, t);
+    applyStyleProperty(PropertyKey::LineTranslateY, line.translate[1], z, t);
+    applyStyleProperty(PropertyKey::LineTranslateAnchor, line.translateAnchor, z, t);
+    applyStyleProperty(PropertyKey::LineWidth, line.width, z, t);
+    applyStyleProperty(PropertyKey::LineOffset, line.offset, z, t);
+    applyStyleProperty(PropertyKey::LineBlur, line.blur, z, t);
+    applyStyleProperty(PropertyKey::LineDashLand, line.dash_array[0], z, t);
+    applyStyleProperty(PropertyKey::LineDashGap, line.dash_array[1], z, t);
+    applyStyleProperty(PropertyKey::LineImage, line.image, z, t);
+}
+
+void StyleLayer::updateProperties(float z, const timestamp t) {
+    if (layers) {
+        layers->updateProperties(z, t);
+    }
+
+    // Accomodate for different tile size.
+    if (bucket && bucket->source) {
+        z += std::log(bucket->source->tile_size / 256.0f) / M_LN2;
+    }
+
+    if (layers) {
+        applyStyleProperties<CompositeProperties>(z, t);
+    } else if (bucket) {
+        switch (bucket->type) {
+            case BucketType::Fill: applyStyleProperties<FillProperties>(z, t); break;
+            case BucketType::Line: applyStyleProperties<LineProperties>(z, t); break;
+            case BucketType::Icon: applyStyleProperties<IconProperties>(z, t); break;
+            case BucketType::Text: applyStyleProperties<TextProperties>(z, t); break;
+            case BucketType::Raster: applyStyleProperties<RasterProperties>(z, t); break;
+            default: properties.set<std::false_type>(); break;
+        }
+    } else {
+        return applyStyleProperties<BackgroundProperties>(z, t);
+    }
+}
+
+
 }
diff --git a/src/style/style_layer_group.cpp b/src/style/style_layer_group.cpp
index 2f0fdf39e0..bb19df45be 100644
--- a/src/style/style_layer_group.cpp
+++ b/src/style/style_layer_group.cpp
@@ -11,4 +11,12 @@ void StyleLayerGroup::setClasses(const std::vector<std::string> &class_names, ti
     }
 }
 
+void StyleLayerGroup::updateProperties(float z, timestamp t) {
+    for (const std::shared_ptr<StyleLayer> &layer: layers) {
+        if (layer) {
+            layer->updateProperties(z, t);
+        }
+    }
+}
+
 }
diff --git a/src/style/style_parser.cpp b/src/style/style_parser.cpp
index 7fa23cc914..c2f1ab5ec3 100644
--- a/src/style/style_parser.cpp
+++ b/src/style/style_parser.cpp
@@ -172,38 +172,152 @@ void StyleParser::parseSources(JSVal value) {
 
 #pragma mark - Parse Style Properties
 
-template<> bool StyleParser::parseStyleProperty<bool>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
-    if (!value.HasMember(property_name)) {
-        return false;
+Color parseColor(JSVal value) {
+    if (!value.IsString()) {
+        fprintf(stderr, "[WARNING] color value must be a string\n");
+        return Color{{ 0, 0, 0, 0 }};
     }
 
-    JSVal rvalue = replaceConstant(value[property_name]);
-    if (!rvalue.IsBool()) {
-        fprintf(stderr, "[WARNING] value of '%s' must be a boolean\n", property_name);
+    CSSColorParser::Color css_color = CSSColorParser::parse({ value.GetString(), value.GetStringLength() });
+
+    // Premultiply the color.
+    const float factor = css_color.a / 255;
+
+    return Color{{(float)css_color.r * factor,
+                  (float)css_color.g * factor,
+                  (float)css_color.b * factor,
+                  css_color.a}};
+}
+
+template <>
+bool StyleParser::parseFunctionArgument(JSVal value) {
+    JSVal rvalue = replaceConstant(value);
+    if (rvalue.IsBool()) {
+        return rvalue.GetBool();
+    } else if (rvalue.IsNumber()) {
+        return rvalue.GetDouble();
+    } else {
+        fprintf(stderr, "[WARNING] function argument must be a boolean or numeric value");
         return false;
     }
+}
 
-    klass.set(key, bool(value.GetBool()));
-    return true;
+template <>
+float StyleParser::parseFunctionArgument(JSVal value) {
+    JSVal rvalue = replaceConstant(value);
+    if (rvalue.IsNumber()) {
+        return rvalue.GetDouble();
+    } else {
+        fprintf(stderr, "[WARNING] function argument must be a numeric value");
+        return 0.0f;
+    }
 }
 
+template <>
+Color StyleParser::parseFunctionArgument(JSVal value) {
+    JSVal rvalue = replaceConstant(value);
+    return parseColor(rvalue);
+}
 
-template<> bool StyleParser::parseStyleProperty<std::string>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
-    if (!value.HasMember(property_name)) {
+template <typename T>
+bool StyleParser::parseFunction(PropertyKey key, ClassProperties &klass, JSVal value) {
+    if (!value.HasMember("fn")) {
+        fprintf(stderr, "[WARNING] function must specify a function name\n");
         return false;
     }
 
-    JSVal rvalue = replaceConstant(value[property_name]);
-    if (!rvalue.IsString()) {
-        fprintf(stderr, "[WARNING] value of '%s' must be a string\n", property_name);
+    JSVal value_fn = value["fn"];
+    if (!value_fn.IsString()) {
+        fprintf(stderr, "[WARNING] function must specify a function type\n");
         return false;
     }
 
-    klass.set(key, std::string { rvalue.GetString(), rvalue.GetStringLength() });
-    return true;
+    const std::string type { value_fn.GetString(), value_fn.GetStringLength() };
+
+    if (type == "linear") {
+        if (!value.HasMember("z")) {
+            fprintf(stderr, "[WARNING] linear function must specify a base zoom level\n");
+            return false;
+        }
+        if (!value.HasMember("val")) {
+            fprintf(stderr, "[WARNING] linear function must specify a base value\n");
+            return false;
+        }
+        const float z_base = parseFunctionArgument<float>(value["z"]);
+        const T val = parseFunctionArgument<T>(value["val"]);
+        const float slope = value.HasMember("slope") ? parseFunctionArgument<float>(value["slope"]) : 1;
+        const T min = value.HasMember("min") ? parseFunctionArgument<T>(value["min"]) : T();
+        const T max = value.HasMember("max") ? parseFunctionArgument<T>(value["max"]) : T();
+        klass.set(key, LinearFunction<T>(val, z_base, slope, min, max));
+        return true;
+    }
+    else if (type == "exponential") {
+        if (!value.HasMember("z")) {
+            fprintf(stderr, "[WARNING] exponential function must specify a base zoom level\n");
+            return false;
+        }
+        if (!value.HasMember("val")) {
+            fprintf(stderr, "[WARNING] exponential function must specify a base value\n");
+            return false;
+        }
+        const float z_base = parseFunctionArgument<float>(value["z"]);
+        const T val = parseFunctionArgument<T>(value["val"]);
+        const float slope = value.HasMember("slope") ? parseFunctionArgument<float>(value["slope"]) : 1;
+        const T min = value.HasMember("min") ? parseFunctionArgument<T>(value["min"]) : T();
+        const T max = value.HasMember("max") ? parseFunctionArgument<T>(value["max"]) : T();
+        klass.set(key, ExponentialFunction<T>(val, z_base, slope, min, max));
+        return true;
+
+    }
+    else if (type == "stops") {
+        if (!value.HasMember("stops")) {
+            fprintf(stderr, "[WARNING] stops function must specify a stops array\n");
+            return false;
+        }
+
+        JSVal value_stops = value["stops"];
+        if (!value_stops.IsArray()) {
+            fprintf(stderr, "[WARNING] stops function must specify a stops array\n");
+            return false;
+        }
+
+        std::vector<std::pair<float, T>> stops;
+        for (rapidjson::SizeType i = 0; i < value.Size(); ++i) {
+            JSVal stop = value[i];
+            if (stop.IsObject()) {
+                if (!stop.HasMember("z")) {
+                    fprintf(stderr, "[WARNING] stop must have zoom level specification\n");
+                    return false;
+                }
+                if (!stop.HasMember("val")) {
+                    fprintf(stderr, "[WARNING] stop must have value specification\n");
+                    return false;
+                }
+
+                JSVal z = stop["z"];
+                if (!z.IsNumber()) {
+                    fprintf(stderr, "[WARNING] zoom level in stop must be a number\n");
+                    return false;
+                }
+
+                stops.emplace_back(z.GetDouble(), parseFunctionArgument<T>(stop["val"]));
+            } else {
+                fprintf(stderr, "[WARNING] function argument must be a numeric value\n");
+                return false;
+            }
+        }
+
+        klass.set(key, StopsFunction<T>(stops));
+        return true;
+    }
+    else {
+        fprintf(stderr, "[WARNING] function type '%s' is unknown\n", type.c_str());
+    }
+
+    return false;
 }
 
-template<> bool StyleParser::parseStyleProperty<TranslateAnchorType>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
+template<> bool StyleParser::parseStyleProperty<std::string>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
     if (!value.HasMember(property_name)) {
         return false;
     }
@@ -214,12 +328,11 @@ template<> bool StyleParser::parseStyleProperty<TranslateAnchorType>(const char
         return false;
     }
 
-    klass.set(key, parseTranslateAnchorType({ rvalue.GetString(), rvalue.GetStringLength() }));
+    klass.set(key, std::string { rvalue.GetString(), rvalue.GetStringLength() });
     return true;
 }
 
-
-template<> bool StyleParser::parseStyleProperty<RotateAnchorType>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
+template<> bool StyleParser::parseStyleProperty<TranslateAnchorType>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
     if (!value.HasMember(property_name)) {
         return false;
     }
@@ -230,11 +343,11 @@ template<> bool StyleParser::parseStyleProperty<RotateAnchorType>(const char *pr
         return false;
     }
 
-    klass.set(key, parseRotateAnchorType({ rvalue.GetString(), rvalue.GetStringLength() }));
+    klass.set(key, parseTranslateAnchorType({ rvalue.GetString(), rvalue.GetStringLength() }));
     return true;
 }
 
-template<> bool StyleParser::parseStyleProperty<Color>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
+template<> bool StyleParser::parseStyleProperty<RotateAnchorType>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
     if (!value.HasMember(property_name)) {
         return false;
     }
@@ -245,15 +358,7 @@ template<> bool StyleParser::parseStyleProperty<Color>(const char *property_name
         return false;
     }
 
-    CSSColorParser::Color css_color = CSSColorParser::parse({ rvalue.GetString(), rvalue.GetStringLength() });
-
-    // Premultiply the color.
-    const float factor = css_color.a / 255;
-
-    klass.set(key, Color{{(float)css_color.r * factor,
-             (float)css_color.g * factor,
-             (float)css_color.b * factor,
-             css_color.a}});
+    klass.set(key, parseRotateAnchorType({ rvalue.GetString(), rvalue.GetStringLength() }));
     return true;
 }
 
@@ -281,82 +386,64 @@ template <> bool StyleParser::parseStyleProperty<PropertyTransition>(const char
     return true;
 }
 
-
-FunctionProperty::fn parseFunctionType(JSVal type) {
-    if (type.IsString()) {
-        std::string t { type.GetString(), type.GetStringLength() };
-        if (t == "constant") {
-            return &functions::constant;
-        } else if (t == "linear") {
-            return &functions::linear;
-        } else if (t == "stops") {
-            return &functions::stops;
-        } else if (t == "exponential") {
-            return &functions::exponential;
-        } else if (t == "min") {
-            return &functions::min;
-        } else if (t == "max") {
-            return &functions::max;
+template<> bool StyleParser::parseStyleProperty<Function<bool>>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
+    if (!value.HasMember(property_name)) {
+        return false;
+    } else {
+        JSVal rvalue = replaceConstant(value[property_name]);
+        if (rvalue.IsObject()) {
+            return parseFunction<bool>(key, klass, rvalue);
+        } else if (rvalue.IsNumber()) {
+            klass.set(key, bool(rvalue.GetDouble()));
+            return true;
+        } else if (rvalue.IsBool()) {
+            klass.set(key, bool(rvalue.GetBool()));
+            return true;
         } else {
-            throw Style::exception("unknown function type");
+            fprintf(stderr, "[WARNING] value of '%s' must be a boolean, or a boolean function\n", property_name);
+            return false;
         }
-    } else {
-        throw Style::exception("function type must be a string");
     }
 }
 
-template<> bool StyleParser::parseStyleProperty<FunctionProperty>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
+template<> bool StyleParser::parseStyleProperty<Function<float>>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
     if (!value.HasMember(property_name)) {
         return false;
-    }
-
-    JSVal rvalue = replaceConstant(value[property_name]);
-    FunctionProperty property;
-
-    if (rvalue.IsArray()) {
-        if (rvalue.Size() < 1) {
-            fprintf(stderr, "[WARNING] function of '%s' does not have arguments\n", property_name);
+    } else {
+        JSVal rvalue = replaceConstant(value[property_name]);
+        if (rvalue.IsObject()) {
+            return parseFunction<float>(key, klass, rvalue);
+        } else if (rvalue.IsNumber()) {
+            klass.set(key, float(rvalue.GetDouble()));
+            return true;
+        } else if (rvalue.IsBool()) {
+            klass.set(key, float(rvalue.GetBool()));
+            return true;
+        } else {
+            fprintf(stderr, "[WARNING] value of '%s' must be a number, or a number function\n", property_name);
             return false;
         }
+    }
+}
 
-        property.function = parseFunctionType(rvalue[(rapidjson::SizeType)0]);
-        for (rapidjson::SizeType i = 1; i < rvalue.Size(); ++i) {
-            JSVal stop = rvalue[i];
-            if (stop.IsObject()) {
-                if (!stop.HasMember("z")) {
-                    throw Style::exception("stop must have zoom level specification");
-                }
-                JSVal z = stop["z"];
-                if (!z.IsNumber()) {
-                    throw Style::exception("zoom level in stops must be a number");
-                }
-                property.values.push_back(z.GetDouble());
-
-                if (!stop.HasMember("val")) {
-                    throw Style::exception("stop must have value specification");
-                }
-                JSVal val = stop["val"];
-                if (!val.IsNumber()) {
-                    throw Style::exception("value in stops must be a number");
-                }
-                property.values.push_back(val.GetDouble());
-            } else if (stop.IsNumber()) {
-                property.values.push_back(stop.GetDouble());
-            } else if (stop.IsBool()) {
-                property.values.push_back(stop.GetBool());
-            } else {
-                throw Style::exception("function argument must be a numeric value");
-            }
+template<> bool StyleParser::parseStyleProperty<Function<Color>>(const char *property_name, PropertyKey key, ClassProperties &klass, JSVal value) {
+    if (!value.HasMember(property_name)) {
+        return false;
+    } else {
+        JSVal rvalue = replaceConstant(value[property_name]);
+        if (rvalue.IsObject()) {
+            return parseFunction<Color>(key, klass, rvalue);
+        } else if (rvalue.IsString()) {
+            klass.set(key, parseColor(rvalue));
+            return true;
+        } else {
+            fprintf(stderr, "[WARNING] value of '%s' must be a color, or a color function\n", property_name);
+            return false;
         }
-    } else if (rvalue.IsNumber()) {
-        property.function = &functions::constant;
-        property.values.push_back(rvalue.GetDouble());
     }
-
-    klass.set(key, std::move(property));
-    return true;
 }
 
+
 template <typename T>
 bool StyleParser::parseStyleProperty(const char *property_name, const std::vector<PropertyKey> &keys, ClassProperties &klass, JSVal value) {
     if (value.HasMember(property_name)) {
@@ -490,84 +577,84 @@ void StyleParser::parseStyles(JSVal value, std::map<ClassID, ClassProperties> &s
 void StyleParser::parseStyle(JSVal value, ClassProperties &klass) {
     using Key = PropertyKey;
 
-    parseStyleProperty<FunctionProperty>("fill-enabled", Key::FillEnabled, klass, value);
+    parseStyleProperty<Function<bool>>("fill-enabled", Key::FillEnabled, klass, value);
     parseStyleProperty<PropertyTransition>("transition-fill-enabled", Key::FillEnabled, klass, value);
-    parseStyleProperty<FunctionProperty>("fill-antialias", Key::FillAntialias, klass, value);
-    parseStyleProperty<FunctionProperty>("fill-opacity", Key::FillOpacity, klass, value);
+    parseStyleProperty<Function<bool>>("fill-antialias", Key::FillAntialias, klass, value);
+    parseStyleProperty<Function<float>>("fill-opacity", Key::FillOpacity, klass, value);
     parseStyleProperty<PropertyTransition>("transition-fill-opacity", Key::FillOpacity, klass, value);
-    parseStyleProperty<Color>("fill-color", Key::FillColor, klass, value);
+    parseStyleProperty<Function<Color>>("fill-color", Key::FillColor, klass, value);
     parseStyleProperty<PropertyTransition>("transition-fill-color", Key::FillColor, klass, value);
-    parseStyleProperty<Color>("fill-outline-color", Key::FillOutlineColor, klass, value);
+    parseStyleProperty<Function<Color>>("fill-outline-color", Key::FillOutlineColor, klass, value);
     parseStyleProperty<PropertyTransition>("transition-fill-outline-color", Key::FillOutlineColor, klass, value);
-    parseStyleProperty<FunctionProperty>("fill-translate", { Key::FillTranslateX, Key::FillTranslateY }, klass, value);
+    parseStyleProperty<Function<float>>("fill-translate", { Key::FillTranslateX, Key::FillTranslateY }, klass, value);
     parseStyleProperty<PropertyTransition>("transition-fill-translate", Key::FillTranslate, klass, value);
     parseStyleProperty<TranslateAnchorType>("fill-translate-anchor", Key::FillTranslateAnchor, klass, value);
     parseStyleProperty<std::string>("fill-image", Key::FillImage, klass, value);
 
-    parseStyleProperty<FunctionProperty>("line-enabled", Key::LineEnabled, klass, value);
+    parseStyleProperty<Function<bool>>("line-enabled", Key::LineEnabled, klass, value);
     parseStyleProperty<PropertyTransition>("transition-line-enabled", Key::LineEnabled, klass, value);
-    parseStyleProperty<FunctionProperty>("line-opacity", Key::LineOpacity, klass, value);
+    parseStyleProperty<Function<float>>("line-opacity", Key::LineOpacity, klass, value);
     parseStyleProperty<PropertyTransition>("transition-line-opacity", Key::LineOpacity, klass, value);
-    parseStyleProperty<Color>("line-color", Key::LineColor, klass, value);
+    parseStyleProperty<Function<Color>>("line-color", Key::LineColor, klass, value);
     parseStyleProperty<PropertyTransition>("transition-line-color", Key::LineColor, klass, value);
-    parseStyleProperty<FunctionProperty>("line-translate", { Key::LineTranslateX, Key::LineTranslateY }, klass, value);
+    parseStyleProperty<Function<float>>("line-translate", { Key::LineTranslateX, Key::LineTranslateY }, klass, value);
     parseStyleProperty<PropertyTransition>("transition-line-translate", Key::LineTranslate, klass, value);
     parseStyleProperty<TranslateAnchorType>("line-translate-anchor", Key::LineTranslateAnchor, klass, value);
-    parseStyleProperty<FunctionProperty>("line-width", Key::LineWidth, klass, value);
+    parseStyleProperty<Function<float>>("line-width", Key::LineWidth, klass, value);
     parseStyleProperty<PropertyTransition>("transition-line-width", Key::LineWidth, klass, value);
-    parseStyleProperty<FunctionProperty>("line-offset", Key::LineOffset, klass, value);
+    parseStyleProperty<Function<float>>("line-offset", Key::LineOffset, klass, value);
     parseStyleProperty<PropertyTransition>("transition-line-offset", Key::LineOffset, klass, value);
-    parseStyleProperty<FunctionProperty>("line-blur", Key::LineBlur, klass, value);
+    parseStyleProperty<Function<float>>("line-blur", Key::LineBlur, klass, value);
     parseStyleProperty<PropertyTransition>("transition-line-blur", Key::LineBlur, klass, value);
-    parseStyleProperty<FunctionProperty>("line-dasharray", { Key::LineDashLand, Key::LineDashGap }, klass, value);
+    parseStyleProperty<Function<float>>("line-dasharray", { Key::LineDashLand, Key::LineDashGap }, klass, value);
     parseStyleProperty<PropertyTransition>("transition-line-dasharray", Key::LineDashArray, klass, value);
     parseStyleProperty<std::string>("line-image", Key::LineImage, klass, value);
 
-    parseStyleProperty<FunctionProperty>("icon-enabled", Key::IconEnabled, klass, value);
+    parseStyleProperty<Function<bool>>("icon-enabled", Key::IconEnabled, klass, value);
     parseStyleProperty<PropertyTransition>("transition-icon-enabled", Key::IconEnabled, klass, value);
-    parseStyleProperty<FunctionProperty>("icon-opacity", Key::IconOpacity, klass, value);
+    parseStyleProperty<Function<float>>("icon-opacity", Key::IconOpacity, klass, value);
     parseStyleProperty<PropertyTransition>("transition-icon-opacity", Key::IconOpacity, klass, value);
-    parseStyleProperty<FunctionProperty>("icon-rotate", Key::IconRotate, klass, value);
+    parseStyleProperty<Function<float>>("icon-rotate", Key::IconRotate, klass, value);
     parseStyleProperty<RotateAnchorType>("icon-rotate-anchor", Key::IconRotateAnchor, klass, value);
 
-    parseStyleProperty<FunctionProperty>("text-enabled", Key::TextEnabled, klass, value);
+    parseStyleProperty<Function<bool>>("text-enabled", Key::TextEnabled, klass, value);
     parseStyleProperty<PropertyTransition>("transition-text-enabled", Key::TextEnabled, klass, value);
-    parseStyleProperty<FunctionProperty>("text-opacity", Key::TextOpacity, klass, value);
+    parseStyleProperty<Function<float>>("text-opacity", Key::TextOpacity, klass, value);
     parseStyleProperty<PropertyTransition>("transition-text-opacity", Key::TextOpacity, klass, value);
-    parseStyleProperty<FunctionProperty>("text-size", Key::TextSize, klass, value);
+    parseStyleProperty<Function<float>>("text-size", Key::TextSize, klass, value);
     parseStyleProperty<PropertyTransition>("transition-text-size", Key::TextSize, klass, value);
-    parseStyleProperty<Color>("text-color", Key::TextColor, klass, value);
+    parseStyleProperty<Function<Color>>("text-color", Key::TextColor, klass, value);
     parseStyleProperty<PropertyTransition>("transition-text-color", Key::TextColor, klass, value);
-    parseStyleProperty<Color>("text-halo-color", Key::TextHaloColor, klass, value);
+    parseStyleProperty<Function<Color>>("text-halo-color", Key::TextHaloColor, klass, value);
     parseStyleProperty<PropertyTransition>("transition-text-halo-color", Key::TextHaloColor, klass, value);
-    parseStyleProperty<FunctionProperty>("text-halo-width", Key::TextHaloWidth, klass, value);
+    parseStyleProperty<Function<float>>("text-halo-width", Key::TextHaloWidth, klass, value);
     parseStyleProperty<PropertyTransition>("transition-text-halo-width", Key::TextHaloWidth, klass, value);
-    parseStyleProperty<FunctionProperty>("text-halo-blur", Key::TextHaloBlur, klass, value);
+    parseStyleProperty<Function<float>>("text-halo-blur", Key::TextHaloBlur, klass, value);
     parseStyleProperty<PropertyTransition>("transition-text-halo-blur", Key::TextHaloBlur, klass, value);
 
-    parseStyleProperty<FunctionProperty>("composite-enabled", Key::CompositeEnabled, klass, value);
+    parseStyleProperty<Function<bool>>("composite-enabled", Key::CompositeEnabled, klass, value);
     parseStyleProperty<PropertyTransition>("transition-composite-enabled", Key::CompositeEnabled, klass, value);
-    parseStyleProperty<FunctionProperty>("composite-opacity", Key::CompositeOpacity, klass, value);
+    parseStyleProperty<Function<float>>("composite-opacity", Key::CompositeOpacity, klass, value);
     parseStyleProperty<PropertyTransition>("transition-composite-opacity", Key::CompositeOpacity, klass, value);
 
-    parseStyleProperty<FunctionProperty>("raster-enabled", Key::RasterEnabled, klass, value);
+    parseStyleProperty<Function<bool>>("raster-enabled", Key::RasterEnabled, klass, value);
     parseStyleProperty<PropertyTransition>("transition-raster-enabled", Key::RasterEnabled, klass, value);
-    parseStyleProperty<FunctionProperty>("raster-opacity", Key::RasterOpacity, klass, value);
+    parseStyleProperty<Function<float>>("raster-opacity", Key::RasterOpacity, klass, value);
     parseStyleProperty<PropertyTransition>("transition-raster-opacity", Key::RasterOpacity, klass, value);
-    parseStyleProperty<FunctionProperty>("raster-spin", Key::RasterSpin, klass, value);
+    parseStyleProperty<Function<float>>("raster-spin", Key::RasterSpin, klass, value);
     parseStyleProperty<PropertyTransition>("transition-raster-spin", Key::RasterSpin, klass, value);
-    parseStyleProperty<FunctionProperty>("raster-brightness-low", Key::RasterBrightnessLow, klass, value);
+    parseStyleProperty<Function<float>>("raster-brightness-low", Key::RasterBrightnessLow, klass, value);
     parseStyleProperty<PropertyTransition>("transition-raster-brightness-low", Key::RasterBrightnessLow, klass, value);
-    parseStyleProperty<FunctionProperty>("raster-brightness-high", Key::RasterBrightnessHigh, klass, value);
+    parseStyleProperty<Function<float>>("raster-brightness-high", Key::RasterBrightnessHigh, klass, value);
     parseStyleProperty<PropertyTransition>("transition-raster-brightness-high", Key::RasterBrightnessHigh, klass, value);
-    parseStyleProperty<FunctionProperty>("raster-saturation", Key::RasterSaturation, klass, value);
+    parseStyleProperty<Function<float>>("raster-saturation", Key::RasterSaturation, klass, value);
     parseStyleProperty<PropertyTransition>("transition-raster-saturation", Key::RasterSaturation, klass, value);
-    parseStyleProperty<FunctionProperty>("raster-contrast", Key::RasterContrast, klass, value);
+    parseStyleProperty<Function<float>>("raster-contrast", Key::RasterContrast, klass, value);
     parseStyleProperty<PropertyTransition>("transition-raster-contrast", Key::RasterContrast, klass, value);
-    parseStyleProperty<FunctionProperty>("raster-fade", Key::RasterFade, klass, value);
+    parseStyleProperty<Function<float>>("raster-fade", Key::RasterFade, klass, value);
     parseStyleProperty<PropertyTransition>("transition-raster-fade", Key::RasterFade, klass, value);
 
-    parseStyleProperty<Color>("background-color", Key::BackgroundColor, klass, value);
+    parseStyleProperty<Function<Color>>("background-color", Key::BackgroundColor, klass, value);
 }
 
 std::unique_ptr<const RasterizeProperties> StyleParser::parseRasterize(JSVal value) {