16 files changed, 183 insertions, 144 deletions

diff --git a/src/mbgl/style/layers/background_layer.cpp b/src/mbgl/style/layers/background_layer.cpp
index 9187784452..6629044018 100644
--- a/src/mbgl/style/layers/background_layer.cpp
+++ b/src/mbgl/style/layers/background_layer.cpp
@@ -64,7 +64,7 @@ void BackgroundLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::StringB
 // Paint properties
 
 PropertyValue<Color> BackgroundLayer::getDefaultBackgroundColor() {
-    return { Color::black() };
+    return {Color::black()};
 }
 
 const PropertyValue<Color>& BackgroundLayer::getBackgroundColor() const {
@@ -91,7 +91,7 @@ TransitionOptions BackgroundLayer::getBackgroundColorTransition() const {
 }
 
 PropertyValue<float> BackgroundLayer::getDefaultBackgroundOpacity() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& BackgroundLayer::getBackgroundOpacity() const {
@@ -117,15 +117,15 @@ TransitionOptions BackgroundLayer::getBackgroundOpacityTransition() const {
     return impl().paint.template get<BackgroundOpacity>().options;
 }
 
-PropertyValue<std::string> BackgroundLayer::getDefaultBackgroundPattern() {
-    return { "" };
+PropertyValue<expression::Image> BackgroundLayer::getDefaultBackgroundPattern() {
+    return {{}};
 }
 
-const PropertyValue<std::string>& BackgroundLayer::getBackgroundPattern() const {
+const PropertyValue<expression::Image>& BackgroundLayer::getBackgroundPattern() const {
     return impl().paint.template get<BackgroundPattern>().value;
 }
 
-void BackgroundLayer::setBackgroundPattern(const PropertyValue<std::string>& value) {
+void BackgroundLayer::setBackgroundPattern(const PropertyValue<expression::Image>& value) {
     if (value == getBackgroundPattern())
         return;
     auto impl_ = mutableImpl();
@@ -208,7 +208,8 @@ optional<Error> BackgroundLayer::setPaintProperty(const std::string& name, const
     
     if (property == Property::BackgroundPattern) {
         Error error;
-        optional<PropertyValue<std::string>> typedValue = convert<PropertyValue<std::string>>(value, error, false, false);
+        optional<PropertyValue<expression::Image>> typedValue =
+            convert<PropertyValue<expression::Image>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
diff --git a/src/mbgl/style/layers/background_layer_properties.hpp b/src/mbgl/style/layers/background_layer_properties.hpp
index 11328f78bb..b926295c00 100644
--- a/src/mbgl/style/layers/background_layer_properties.hpp
+++ b/src/mbgl/style/layers/background_layer_properties.hpp
@@ -24,8 +24,8 @@ struct BackgroundOpacity : PaintProperty<float> {
     static float defaultValue() { return 1; }
 };
 
-struct BackgroundPattern : CrossFadedPaintProperty<std::string> {
-    static std::string defaultValue() { return ""; }
+struct BackgroundPattern : CrossFadedPaintProperty<expression::Image> {
+    static expression::Image defaultValue() { return {}; }
 };
 
 class BackgroundPaintProperties : public Properties<
diff --git a/src/mbgl/style/layers/circle_layer.cpp b/src/mbgl/style/layers/circle_layer.cpp
index 145d76a9a8..619c58c366 100644
--- a/src/mbgl/style/layers/circle_layer.cpp
+++ b/src/mbgl/style/layers/circle_layer.cpp
@@ -64,7 +64,7 @@ void CircleLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::StringBuffe
 // Paint properties
 
 PropertyValue<float> CircleLayer::getDefaultCircleBlur() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& CircleLayer::getCircleBlur() const {
@@ -91,7 +91,7 @@ TransitionOptions CircleLayer::getCircleBlurTransition() const {
 }
 
 PropertyValue<Color> CircleLayer::getDefaultCircleColor() {
-    return { Color::black() };
+    return {Color::black()};
 }
 
 const PropertyValue<Color>& CircleLayer::getCircleColor() const {
@@ -118,7 +118,7 @@ TransitionOptions CircleLayer::getCircleColorTransition() const {
 }
 
 PropertyValue<float> CircleLayer::getDefaultCircleOpacity() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& CircleLayer::getCircleOpacity() const {
@@ -145,7 +145,7 @@ TransitionOptions CircleLayer::getCircleOpacityTransition() const {
 }
 
 PropertyValue<AlignmentType> CircleLayer::getDefaultCirclePitchAlignment() {
-    return { AlignmentType::Viewport };
+    return {AlignmentType::Viewport};
 }
 
 const PropertyValue<AlignmentType>& CircleLayer::getCirclePitchAlignment() const {
@@ -172,7 +172,7 @@ TransitionOptions CircleLayer::getCirclePitchAlignmentTransition() const {
 }
 
 PropertyValue<CirclePitchScaleType> CircleLayer::getDefaultCirclePitchScale() {
-    return { CirclePitchScaleType::Map };
+    return {CirclePitchScaleType::Map};
 }
 
 const PropertyValue<CirclePitchScaleType>& CircleLayer::getCirclePitchScale() const {
@@ -199,7 +199,7 @@ TransitionOptions CircleLayer::getCirclePitchScaleTransition() const {
 }
 
 PropertyValue<float> CircleLayer::getDefaultCircleRadius() {
-    return { 5 };
+    return {5};
 }
 
 const PropertyValue<float>& CircleLayer::getCircleRadius() const {
@@ -226,7 +226,7 @@ TransitionOptions CircleLayer::getCircleRadiusTransition() const {
 }
 
 PropertyValue<Color> CircleLayer::getDefaultCircleStrokeColor() {
-    return { Color::black() };
+    return {Color::black()};
 }
 
 const PropertyValue<Color>& CircleLayer::getCircleStrokeColor() const {
@@ -253,7 +253,7 @@ TransitionOptions CircleLayer::getCircleStrokeColorTransition() const {
 }
 
 PropertyValue<float> CircleLayer::getDefaultCircleStrokeOpacity() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& CircleLayer::getCircleStrokeOpacity() const {
@@ -280,7 +280,7 @@ TransitionOptions CircleLayer::getCircleStrokeOpacityTransition() const {
 }
 
 PropertyValue<float> CircleLayer::getDefaultCircleStrokeWidth() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& CircleLayer::getCircleStrokeWidth() const {
@@ -307,7 +307,7 @@ TransitionOptions CircleLayer::getCircleStrokeWidthTransition() const {
 }
 
 PropertyValue<std::array<float, 2>> CircleLayer::getDefaultCircleTranslate() {
-    return { {{ 0, 0 }} };
+    return {{{0, 0}}};
 }
 
 const PropertyValue<std::array<float, 2>>& CircleLayer::getCircleTranslate() const {
@@ -334,7 +334,7 @@ TransitionOptions CircleLayer::getCircleTranslateTransition() const {
 }
 
 PropertyValue<TranslateAnchorType> CircleLayer::getDefaultCircleTranslateAnchor() {
-    return { TranslateAnchorType::Map };
+    return {TranslateAnchorType::Map};
 }
 
 const PropertyValue<TranslateAnchorType>& CircleLayer::getCircleTranslateAnchor() const {
@@ -497,7 +497,8 @@ optional<Error> CircleLayer::setPaintProperty(const std::string& name, const Con
     
     if (property == Property::CirclePitchScale) {
         Error error;
-        optional<PropertyValue<CirclePitchScaleType>> typedValue = convert<PropertyValue<CirclePitchScaleType>>(value, error, false, false);
+        optional<PropertyValue<CirclePitchScaleType>> typedValue =
+            convert<PropertyValue<CirclePitchScaleType>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -509,7 +510,8 @@ optional<Error> CircleLayer::setPaintProperty(const std::string& name, const Con
     
     if (property == Property::CircleTranslate) {
         Error error;
-        optional<PropertyValue<std::array<float, 2>>> typedValue = convert<PropertyValue<std::array<float, 2>>>(value, error, false, false);
+        optional<PropertyValue<std::array<float, 2>>> typedValue =
+            convert<PropertyValue<std::array<float, 2>>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -521,7 +523,8 @@ optional<Error> CircleLayer::setPaintProperty(const std::string& name, const Con
     
     if (property == Property::CircleTranslateAnchor) {
         Error error;
-        optional<PropertyValue<TranslateAnchorType>> typedValue = convert<PropertyValue<TranslateAnchorType>>(value, error, false, false);
+        optional<PropertyValue<TranslateAnchorType>> typedValue =
+            convert<PropertyValue<TranslateAnchorType>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
diff --git a/src/mbgl/style/layers/circle_layer_properties.hpp b/src/mbgl/style/layers/circle_layer_properties.hpp
index a5f7a584df..5204421d0b 100644
--- a/src/mbgl/style/layers/circle_layer_properties.hpp
+++ b/src/mbgl/style/layers/circle_layer_properties.hpp
@@ -53,7 +53,7 @@ struct CircleStrokeWidth : DataDrivenPaintProperty<float, attributes::stroke_wid
 };
 
 struct CircleTranslate : PaintProperty<std::array<float, 2>> {
-    static std::array<float, 2> defaultValue() { return {{ 0, 0 }}; }
+    static std::array<float, 2> defaultValue() { return {{0, 0}}; }
 };
 
 struct CircleTranslateAnchor : PaintProperty<TranslateAnchorType> {
diff --git a/src/mbgl/style/layers/fill_extrusion_layer.cpp b/src/mbgl/style/layers/fill_extrusion_layer.cpp
index 87e196926f..e04e192298 100644
--- a/src/mbgl/style/layers/fill_extrusion_layer.cpp
+++ b/src/mbgl/style/layers/fill_extrusion_layer.cpp
@@ -64,7 +64,7 @@ void FillExtrusionLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::Stri
 // Paint properties
 
 PropertyValue<float> FillExtrusionLayer::getDefaultFillExtrusionBase() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& FillExtrusionLayer::getFillExtrusionBase() const {
@@ -91,7 +91,7 @@ TransitionOptions FillExtrusionLayer::getFillExtrusionBaseTransition() const {
 }
 
 PropertyValue<Color> FillExtrusionLayer::getDefaultFillExtrusionColor() {
-    return { Color::black() };
+    return {Color::black()};
 }
 
 const PropertyValue<Color>& FillExtrusionLayer::getFillExtrusionColor() const {
@@ -118,7 +118,7 @@ TransitionOptions FillExtrusionLayer::getFillExtrusionColorTransition() const {
 }
 
 PropertyValue<float> FillExtrusionLayer::getDefaultFillExtrusionHeight() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& FillExtrusionLayer::getFillExtrusionHeight() const {
@@ -145,7 +145,7 @@ TransitionOptions FillExtrusionLayer::getFillExtrusionHeightTransition() const {
 }
 
 PropertyValue<float> FillExtrusionLayer::getDefaultFillExtrusionOpacity() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& FillExtrusionLayer::getFillExtrusionOpacity() const {
@@ -171,15 +171,15 @@ TransitionOptions FillExtrusionLayer::getFillExtrusionOpacityTransition() const
     return impl().paint.template get<FillExtrusionOpacity>().options;
 }
 
-PropertyValue<std::string> FillExtrusionLayer::getDefaultFillExtrusionPattern() {
-    return { "" };
+PropertyValue<expression::Image> FillExtrusionLayer::getDefaultFillExtrusionPattern() {
+    return {{}};
 }
 
-const PropertyValue<std::string>& FillExtrusionLayer::getFillExtrusionPattern() const {
+const PropertyValue<expression::Image>& FillExtrusionLayer::getFillExtrusionPattern() const {
     return impl().paint.template get<FillExtrusionPattern>().value;
 }
 
-void FillExtrusionLayer::setFillExtrusionPattern(const PropertyValue<std::string>& value) {
+void FillExtrusionLayer::setFillExtrusionPattern(const PropertyValue<expression::Image>& value) {
     if (value == getFillExtrusionPattern())
         return;
     auto impl_ = mutableImpl();
@@ -199,7 +199,7 @@ TransitionOptions FillExtrusionLayer::getFillExtrusionPatternTransition() const
 }
 
 PropertyValue<std::array<float, 2>> FillExtrusionLayer::getDefaultFillExtrusionTranslate() {
-    return { {{ 0, 0 }} };
+    return {{{0, 0}}};
 }
 
 const PropertyValue<std::array<float, 2>>& FillExtrusionLayer::getFillExtrusionTranslate() const {
@@ -226,7 +226,7 @@ TransitionOptions FillExtrusionLayer::getFillExtrusionTranslateTransition() cons
 }
 
 PropertyValue<TranslateAnchorType> FillExtrusionLayer::getDefaultFillExtrusionTranslateAnchor() {
-    return { TranslateAnchorType::Map };
+    return {TranslateAnchorType::Map};
 }
 
 const PropertyValue<TranslateAnchorType>& FillExtrusionLayer::getFillExtrusionTranslateAnchor() const {
@@ -253,7 +253,7 @@ TransitionOptions FillExtrusionLayer::getFillExtrusionTranslateAnchorTransition(
 }
 
 PropertyValue<bool> FillExtrusionLayer::getDefaultFillExtrusionVerticalGradient() {
-    return { true };
+    return {true};
 }
 
 const PropertyValue<bool>& FillExtrusionLayer::getFillExtrusionVerticalGradient() const {
@@ -382,7 +382,8 @@ optional<Error> FillExtrusionLayer::setPaintProperty(const std::string& name, co
     
     if (property == Property::FillExtrusionPattern) {
         Error error;
-        optional<PropertyValue<std::string>> typedValue = convert<PropertyValue<std::string>>(value, error, true, false);
+        optional<PropertyValue<expression::Image>> typedValue =
+            convert<PropertyValue<expression::Image>>(value, error, true, false);
         if (!typedValue) {
             return error;
         }
@@ -394,7 +395,8 @@ optional<Error> FillExtrusionLayer::setPaintProperty(const std::string& name, co
     
     if (property == Property::FillExtrusionTranslate) {
         Error error;
-        optional<PropertyValue<std::array<float, 2>>> typedValue = convert<PropertyValue<std::array<float, 2>>>(value, error, false, false);
+        optional<PropertyValue<std::array<float, 2>>> typedValue =
+            convert<PropertyValue<std::array<float, 2>>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -406,7 +408,8 @@ optional<Error> FillExtrusionLayer::setPaintProperty(const std::string& name, co
     
     if (property == Property::FillExtrusionTranslateAnchor) {
         Error error;
-        optional<PropertyValue<TranslateAnchorType>> typedValue = convert<PropertyValue<TranslateAnchorType>>(value, error, false, false);
+        optional<PropertyValue<TranslateAnchorType>> typedValue =
+            convert<PropertyValue<TranslateAnchorType>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
diff --git a/src/mbgl/style/layers/fill_extrusion_layer_properties.hpp b/src/mbgl/style/layers/fill_extrusion_layer_properties.hpp
index 6936d5e0c4..60a2340b0d 100644
--- a/src/mbgl/style/layers/fill_extrusion_layer_properties.hpp
+++ b/src/mbgl/style/layers/fill_extrusion_layer_properties.hpp
@@ -32,12 +32,12 @@ struct FillExtrusionOpacity : PaintProperty<float> {
     static float defaultValue() { return 1; }
 };
 
-struct FillExtrusionPattern : CrossFadedDataDrivenPaintProperty<std::string, attributes::pattern_to, uniforms::pattern_to, attributes::pattern_from, uniforms::pattern_from> {
-    static std::string defaultValue() { return ""; }
+struct FillExtrusionPattern : CrossFadedDataDrivenPaintProperty<expression::Image, attributes::pattern_to, uniforms::pattern_to, attributes::pattern_from, uniforms::pattern_from> {
+    static expression::Image defaultValue() { return {}; }
 };
 
 struct FillExtrusionTranslate : PaintProperty<std::array<float, 2>> {
-    static std::array<float, 2> defaultValue() { return {{ 0, 0 }}; }
+    static std::array<float, 2> defaultValue() { return {{0, 0}}; }
 };
 
 struct FillExtrusionTranslateAnchor : PaintProperty<TranslateAnchorType> {
diff --git a/src/mbgl/style/layers/fill_layer.cpp b/src/mbgl/style/layers/fill_layer.cpp
index e3d6c6c708..ad1f0ae847 100644
--- a/src/mbgl/style/layers/fill_layer.cpp
+++ b/src/mbgl/style/layers/fill_layer.cpp
@@ -64,7 +64,7 @@ void FillLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>
 // Paint properties
 
 PropertyValue<bool> FillLayer::getDefaultFillAntialias() {
-    return { true };
+    return {true};
 }
 
 const PropertyValue<bool>& FillLayer::getFillAntialias() const {
@@ -91,7 +91,7 @@ TransitionOptions FillLayer::getFillAntialiasTransition() const {
 }
 
 PropertyValue<Color> FillLayer::getDefaultFillColor() {
-    return { Color::black() };
+    return {Color::black()};
 }
 
 const PropertyValue<Color>& FillLayer::getFillColor() const {
@@ -118,7 +118,7 @@ TransitionOptions FillLayer::getFillColorTransition() const {
 }
 
 PropertyValue<float> FillLayer::getDefaultFillOpacity() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& FillLayer::getFillOpacity() const {
@@ -145,7 +145,7 @@ TransitionOptions FillLayer::getFillOpacityTransition() const {
 }
 
 PropertyValue<Color> FillLayer::getDefaultFillOutlineColor() {
-    return { {} };
+    return {{}};
 }
 
 const PropertyValue<Color>& FillLayer::getFillOutlineColor() const {
@@ -171,15 +171,15 @@ TransitionOptions FillLayer::getFillOutlineColorTransition() const {
     return impl().paint.template get<FillOutlineColor>().options;
 }
 
-PropertyValue<std::string> FillLayer::getDefaultFillPattern() {
-    return { "" };
+PropertyValue<expression::Image> FillLayer::getDefaultFillPattern() {
+    return {{}};
 }
 
-const PropertyValue<std::string>& FillLayer::getFillPattern() const {
+const PropertyValue<expression::Image>& FillLayer::getFillPattern() const {
     return impl().paint.template get<FillPattern>().value;
 }
 
-void FillLayer::setFillPattern(const PropertyValue<std::string>& value) {
+void FillLayer::setFillPattern(const PropertyValue<expression::Image>& value) {
     if (value == getFillPattern())
         return;
     auto impl_ = mutableImpl();
@@ -199,7 +199,7 @@ TransitionOptions FillLayer::getFillPatternTransition() const {
 }
 
 PropertyValue<std::array<float, 2>> FillLayer::getDefaultFillTranslate() {
-    return { {{ 0, 0 }} };
+    return {{{0, 0}}};
 }
 
 const PropertyValue<std::array<float, 2>>& FillLayer::getFillTranslate() const {
@@ -226,7 +226,7 @@ TransitionOptions FillLayer::getFillTranslateTransition() const {
 }
 
 PropertyValue<TranslateAnchorType> FillLayer::getDefaultFillTranslateAnchor() {
-    return { TranslateAnchorType::Map };
+    return {TranslateAnchorType::Map};
 }
 
 const PropertyValue<TranslateAnchorType>& FillLayer::getFillTranslateAnchor() const {
@@ -351,7 +351,8 @@ optional<Error> FillLayer::setPaintProperty(const std::string& name, const Conve
     
     if (property == Property::FillPattern) {
         Error error;
-        optional<PropertyValue<std::string>> typedValue = convert<PropertyValue<std::string>>(value, error, true, false);
+        optional<PropertyValue<expression::Image>> typedValue =
+            convert<PropertyValue<expression::Image>>(value, error, true, false);
         if (!typedValue) {
             return error;
         }
@@ -363,7 +364,8 @@ optional<Error> FillLayer::setPaintProperty(const std::string& name, const Conve
     
     if (property == Property::FillTranslate) {
         Error error;
-        optional<PropertyValue<std::array<float, 2>>> typedValue = convert<PropertyValue<std::array<float, 2>>>(value, error, false, false);
+        optional<PropertyValue<std::array<float, 2>>> typedValue =
+            convert<PropertyValue<std::array<float, 2>>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -375,7 +377,8 @@ optional<Error> FillLayer::setPaintProperty(const std::string& name, const Conve
     
     if (property == Property::FillTranslateAnchor) {
         Error error;
-        optional<PropertyValue<TranslateAnchorType>> typedValue = convert<PropertyValue<TranslateAnchorType>>(value, error, false, false);
+        optional<PropertyValue<TranslateAnchorType>> typedValue =
+            convert<PropertyValue<TranslateAnchorType>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
diff --git a/src/mbgl/style/layers/fill_layer_properties.hpp b/src/mbgl/style/layers/fill_layer_properties.hpp
index 38ca506199..ad8ed84892 100644
--- a/src/mbgl/style/layers/fill_layer_properties.hpp
+++ b/src/mbgl/style/layers/fill_layer_properties.hpp
@@ -32,12 +32,12 @@ struct FillOutlineColor : DataDrivenPaintProperty<Color, attributes::outline_col
     static Color defaultValue() { return {}; }
 };
 
-struct FillPattern : CrossFadedDataDrivenPaintProperty<std::string, attributes::pattern_to, uniforms::pattern_to, attributes::pattern_from, uniforms::pattern_from> {
-    static std::string defaultValue() { return ""; }
+struct FillPattern : CrossFadedDataDrivenPaintProperty<expression::Image, attributes::pattern_to, uniforms::pattern_to, attributes::pattern_from, uniforms::pattern_from> {
+    static expression::Image defaultValue() { return {}; }
 };
 
 struct FillTranslate : PaintProperty<std::array<float, 2>> {
-    static std::array<float, 2> defaultValue() { return {{ 0, 0 }}; }
+    static std::array<float, 2> defaultValue() { return {{0, 0}}; }
 };
 
 struct FillTranslateAnchor : PaintProperty<TranslateAnchorType> {
diff --git a/src/mbgl/style/layers/heatmap_layer.cpp b/src/mbgl/style/layers/heatmap_layer.cpp
index 332c65c6b4..234dda6c73 100644
--- a/src/mbgl/style/layers/heatmap_layer.cpp
+++ b/src/mbgl/style/layers/heatmap_layer.cpp
@@ -93,7 +93,7 @@ TransitionOptions HeatmapLayer::getHeatmapColorTransition() const {
 }
 
 PropertyValue<float> HeatmapLayer::getDefaultHeatmapIntensity() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& HeatmapLayer::getHeatmapIntensity() const {
@@ -120,7 +120,7 @@ TransitionOptions HeatmapLayer::getHeatmapIntensityTransition() const {
 }
 
 PropertyValue<float> HeatmapLayer::getDefaultHeatmapOpacity() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& HeatmapLayer::getHeatmapOpacity() const {
@@ -147,7 +147,7 @@ TransitionOptions HeatmapLayer::getHeatmapOpacityTransition() const {
 }
 
 PropertyValue<float> HeatmapLayer::getDefaultHeatmapRadius() {
-    return { 30 };
+    return {30};
 }
 
 const PropertyValue<float>& HeatmapLayer::getHeatmapRadius() const {
@@ -174,7 +174,7 @@ TransitionOptions HeatmapLayer::getHeatmapRadiusTransition() const {
 }
 
 PropertyValue<float> HeatmapLayer::getDefaultHeatmapWeight() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& HeatmapLayer::getHeatmapWeight() const {
diff --git a/src/mbgl/style/layers/hillshade_layer.cpp b/src/mbgl/style/layers/hillshade_layer.cpp
index a55c079c49..5d84b7ded3 100644
--- a/src/mbgl/style/layers/hillshade_layer.cpp
+++ b/src/mbgl/style/layers/hillshade_layer.cpp
@@ -64,7 +64,7 @@ void HillshadeLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::StringBu
 // Paint properties
 
 PropertyValue<Color> HillshadeLayer::getDefaultHillshadeAccentColor() {
-    return { Color::black() };
+    return {Color::black()};
 }
 
 const PropertyValue<Color>& HillshadeLayer::getHillshadeAccentColor() const {
@@ -91,7 +91,7 @@ TransitionOptions HillshadeLayer::getHillshadeAccentColorTransition() const {
 }
 
 PropertyValue<float> HillshadeLayer::getDefaultHillshadeExaggeration() {
-    return { 0.5 };
+    return {0.5};
 }
 
 const PropertyValue<float>& HillshadeLayer::getHillshadeExaggeration() const {
@@ -118,7 +118,7 @@ TransitionOptions HillshadeLayer::getHillshadeExaggerationTransition() const {
 }
 
 PropertyValue<Color> HillshadeLayer::getDefaultHillshadeHighlightColor() {
-    return { Color::white() };
+    return {Color::white()};
 }
 
 const PropertyValue<Color>& HillshadeLayer::getHillshadeHighlightColor() const {
@@ -145,7 +145,7 @@ TransitionOptions HillshadeLayer::getHillshadeHighlightColorTransition() const {
 }
 
 PropertyValue<HillshadeIlluminationAnchorType> HillshadeLayer::getDefaultHillshadeIlluminationAnchor() {
-    return { HillshadeIlluminationAnchorType::Viewport };
+    return {HillshadeIlluminationAnchorType::Viewport};
 }
 
 const PropertyValue<HillshadeIlluminationAnchorType>& HillshadeLayer::getHillshadeIlluminationAnchor() const {
@@ -172,7 +172,7 @@ TransitionOptions HillshadeLayer::getHillshadeIlluminationAnchorTransition() con
 }
 
 PropertyValue<float> HillshadeLayer::getDefaultHillshadeIlluminationDirection() {
-    return { 335 };
+    return {335};
 }
 
 const PropertyValue<float>& HillshadeLayer::getHillshadeIlluminationDirection() const {
@@ -199,7 +199,7 @@ TransitionOptions HillshadeLayer::getHillshadeIlluminationDirectionTransition()
 }
 
 PropertyValue<Color> HillshadeLayer::getDefaultHillshadeShadowColor() {
-    return { Color::black() };
+    return {Color::black()};
 }
 
 const PropertyValue<Color>& HillshadeLayer::getHillshadeShadowColor() const {
@@ -320,7 +320,8 @@ optional<Error> HillshadeLayer::setPaintProperty(const std::string& name, const
     
     if (property == Property::HillshadeIlluminationAnchor) {
         Error error;
-        optional<PropertyValue<HillshadeIlluminationAnchorType>> typedValue = convert<PropertyValue<HillshadeIlluminationAnchorType>>(value, error, false, false);
+        optional<PropertyValue<HillshadeIlluminationAnchorType>> typedValue =
+            convert<PropertyValue<HillshadeIlluminationAnchorType>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
diff --git a/src/mbgl/style/layers/layer.cpp.ejs b/src/mbgl/style/layers/layer.cpp.ejs
index 775288264f..a47e5b95b4 100644
--- a/src/mbgl/style/layers/layer.cpp.ejs
+++ b/src/mbgl/style/layers/layer.cpp.ejs
@@ -77,6 +77,15 @@ layerCapabilities['heatmap']        = defaults.require('Source')
                                               .set('TileKind', 'Geometry')
                                               .finalize();
 layerCapabilities['raster']         = defaults.require('Source').set('TileKind', 'Raster').finalize();
+
+// Splits lines that are over 120 characters at the firts occurance of '='.
+const split120Line = line => {
+    if (line.length > 120) {
+        return line.replace('=', '=\n           ');
+    }
+    return line;
+};
+
 %>
 // static
 const LayerTypeInfo* <%- camelize(type) %>Layer::Impl::staticTypeInfo() noexcept {
@@ -155,7 +164,7 @@ void <%- camelize(type) %>Layer::set<%- camelize(property.name) %>(const <%- pro
     std::string rawValue = R"JSON(<%- JSON.stringify(property.default) %>)JSON";
     return *conversion::convertJSON<<%- propertyValueType(property)%>>(rawValue, error);
 <% } else { -%>
-    return { <%- defaultValue(property) %> };
+    return {<%- defaultValue(property) %>};
 <% } -%>
 }
 
@@ -243,7 +252,7 @@ optional<Error> <%- camelize(type) %>Layer::setPaintProperty(const std::string&
     %>
     if (<%- properties.map(p => `property == Property::${camelize(p.name)}`).join(' || ') %>) {
         Error error;
-        <%- key %>;
+        <%- split120Line(key) %>;
         if (!typedValue) {
             return error;
         }
@@ -323,7 +332,7 @@ optional<Error> <%- camelize(type) %>Layer::setLayoutProperty(const std::string&
     %>
     if (<%- properties.map(p => `property == Property::${camelize(p.name)}`).join(' || ') %>) {
         Error error;
-        <%- key %>;
+        <%- split120Line(key) %>;
         if (!typedValue) {
             return error;
         }
diff --git a/src/mbgl/style/layers/line_layer.cpp b/src/mbgl/style/layers/line_layer.cpp
index 309a81ae2b..813ef68dec 100644
--- a/src/mbgl/style/layers/line_layer.cpp
+++ b/src/mbgl/style/layers/line_layer.cpp
@@ -129,7 +129,7 @@ void LineLayer::setLineRoundLimit(const PropertyValue<float>& value) {
 // Paint properties
 
 PropertyValue<float> LineLayer::getDefaultLineBlur() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& LineLayer::getLineBlur() const {
@@ -156,7 +156,7 @@ TransitionOptions LineLayer::getLineBlurTransition() const {
 }
 
 PropertyValue<Color> LineLayer::getDefaultLineColor() {
-    return { Color::black() };
+    return {Color::black()};
 }
 
 const PropertyValue<Color>& LineLayer::getLineColor() const {
@@ -183,7 +183,7 @@ TransitionOptions LineLayer::getLineColorTransition() const {
 }
 
 PropertyValue<std::vector<float>> LineLayer::getDefaultLineDasharray() {
-    return { {  } };
+    return {{}};
 }
 
 const PropertyValue<std::vector<float>>& LineLayer::getLineDasharray() const {
@@ -210,7 +210,7 @@ TransitionOptions LineLayer::getLineDasharrayTransition() const {
 }
 
 PropertyValue<float> LineLayer::getDefaultLineGapWidth() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& LineLayer::getLineGapWidth() const {
@@ -237,7 +237,7 @@ TransitionOptions LineLayer::getLineGapWidthTransition() const {
 }
 
 ColorRampPropertyValue LineLayer::getDefaultLineGradient() {
-    return { {} };
+    return {{}};
 }
 
 const ColorRampPropertyValue& LineLayer::getLineGradient() const {
@@ -264,7 +264,7 @@ TransitionOptions LineLayer::getLineGradientTransition() const {
 }
 
 PropertyValue<float> LineLayer::getDefaultLineOffset() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& LineLayer::getLineOffset() const {
@@ -291,7 +291,7 @@ TransitionOptions LineLayer::getLineOffsetTransition() const {
 }
 
 PropertyValue<float> LineLayer::getDefaultLineOpacity() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& LineLayer::getLineOpacity() const {
@@ -317,15 +317,15 @@ TransitionOptions LineLayer::getLineOpacityTransition() const {
     return impl().paint.template get<LineOpacity>().options;
 }
 
-PropertyValue<std::string> LineLayer::getDefaultLinePattern() {
-    return { "" };
+PropertyValue<expression::Image> LineLayer::getDefaultLinePattern() {
+    return {{}};
 }
 
-const PropertyValue<std::string>& LineLayer::getLinePattern() const {
+const PropertyValue<expression::Image>& LineLayer::getLinePattern() const {
     return impl().paint.template get<LinePattern>().value;
 }
 
-void LineLayer::setLinePattern(const PropertyValue<std::string>& value) {
+void LineLayer::setLinePattern(const PropertyValue<expression::Image>& value) {
     if (value == getLinePattern())
         return;
     auto impl_ = mutableImpl();
@@ -345,7 +345,7 @@ TransitionOptions LineLayer::getLinePatternTransition() const {
 }
 
 PropertyValue<std::array<float, 2>> LineLayer::getDefaultLineTranslate() {
-    return { {{ 0, 0 }} };
+    return {{{0, 0}}};
 }
 
 const PropertyValue<std::array<float, 2>>& LineLayer::getLineTranslate() const {
@@ -372,7 +372,7 @@ TransitionOptions LineLayer::getLineTranslateTransition() const {
 }
 
 PropertyValue<TranslateAnchorType> LineLayer::getDefaultLineTranslateAnchor() {
-    return { TranslateAnchorType::Map };
+    return {TranslateAnchorType::Map};
 }
 
 const PropertyValue<TranslateAnchorType>& LineLayer::getLineTranslateAnchor() const {
@@ -399,7 +399,7 @@ TransitionOptions LineLayer::getLineTranslateAnchorTransition() const {
 }
 
 PropertyValue<float> LineLayer::getDefaultLineWidth() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& LineLayer::getLineWidth() const {
@@ -552,7 +552,8 @@ optional<Error> LineLayer::setPaintProperty(const std::string& name, const Conve
     
     if (property == Property::LineDasharray) {
         Error error;
-        optional<PropertyValue<std::vector<float>>> typedValue = convert<PropertyValue<std::vector<float>>>(value, error, false, false);
+        optional<PropertyValue<std::vector<float>>> typedValue =
+            convert<PropertyValue<std::vector<float>>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -576,7 +577,8 @@ optional<Error> LineLayer::setPaintProperty(const std::string& name, const Conve
     
     if (property == Property::LinePattern) {
         Error error;
-        optional<PropertyValue<std::string>> typedValue = convert<PropertyValue<std::string>>(value, error, true, false);
+        optional<PropertyValue<expression::Image>> typedValue =
+            convert<PropertyValue<expression::Image>>(value, error, true, false);
         if (!typedValue) {
             return error;
         }
@@ -588,7 +590,8 @@ optional<Error> LineLayer::setPaintProperty(const std::string& name, const Conve
     
     if (property == Property::LineTranslate) {
         Error error;
-        optional<PropertyValue<std::array<float, 2>>> typedValue = convert<PropertyValue<std::array<float, 2>>>(value, error, false, false);
+        optional<PropertyValue<std::array<float, 2>>> typedValue =
+            convert<PropertyValue<std::array<float, 2>>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -600,7 +603,8 @@ optional<Error> LineLayer::setPaintProperty(const std::string& name, const Conve
     
     if (property == Property::LineTranslateAnchor) {
         Error error;
-        optional<PropertyValue<TranslateAnchorType>> typedValue = convert<PropertyValue<TranslateAnchorType>>(value, error, false, false);
+        optional<PropertyValue<TranslateAnchorType>> typedValue =
+            convert<PropertyValue<TranslateAnchorType>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
diff --git a/src/mbgl/style/layers/line_layer_properties.hpp b/src/mbgl/style/layers/line_layer_properties.hpp
index 2ecbb10993..29ba9ec641 100644
--- a/src/mbgl/style/layers/line_layer_properties.hpp
+++ b/src/mbgl/style/layers/line_layer_properties.hpp
@@ -45,7 +45,7 @@ struct LineColor : DataDrivenPaintProperty<Color, attributes::color, uniforms::c
 };
 
 struct LineDasharray : CrossFadedPaintProperty<std::vector<float>> {
-    static std::vector<float> defaultValue() { return {  }; }
+    static std::vector<float> defaultValue() { return {}; }
 };
 
 struct LineFloorWidth : DataDrivenPaintProperty<float, attributes::floorwidth, uniforms::floorwidth> {
@@ -68,12 +68,12 @@ struct LineOpacity : DataDrivenPaintProperty<float, attributes::opacity, uniform
     static float defaultValue() { return 1; }
 };
 
-struct LinePattern : CrossFadedDataDrivenPaintProperty<std::string, attributes::pattern_to, uniforms::pattern_to, attributes::pattern_from, uniforms::pattern_from> {
-    static std::string defaultValue() { return ""; }
+struct LinePattern : CrossFadedDataDrivenPaintProperty<expression::Image, attributes::pattern_to, uniforms::pattern_to, attributes::pattern_from, uniforms::pattern_from> {
+    static expression::Image defaultValue() { return {}; }
 };
 
 struct LineTranslate : PaintProperty<std::array<float, 2>> {
-    static std::array<float, 2> defaultValue() { return {{ 0, 0 }}; }
+    static std::array<float, 2> defaultValue() { return {{0, 0}}; }
 };
 
 struct LineTranslateAnchor : PaintProperty<TranslateAnchorType> {
diff --git a/src/mbgl/style/layers/raster_layer.cpp b/src/mbgl/style/layers/raster_layer.cpp
index 359e502f3e..b990409886 100644
--- a/src/mbgl/style/layers/raster_layer.cpp
+++ b/src/mbgl/style/layers/raster_layer.cpp
@@ -64,7 +64,7 @@ void RasterLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::StringBuffe
 // Paint properties
 
 PropertyValue<float> RasterLayer::getDefaultRasterBrightnessMax() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& RasterLayer::getRasterBrightnessMax() const {
@@ -91,7 +91,7 @@ TransitionOptions RasterLayer::getRasterBrightnessMaxTransition() const {
 }
 
 PropertyValue<float> RasterLayer::getDefaultRasterBrightnessMin() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& RasterLayer::getRasterBrightnessMin() const {
@@ -118,7 +118,7 @@ TransitionOptions RasterLayer::getRasterBrightnessMinTransition() const {
 }
 
 PropertyValue<float> RasterLayer::getDefaultRasterContrast() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& RasterLayer::getRasterContrast() const {
@@ -145,7 +145,7 @@ TransitionOptions RasterLayer::getRasterContrastTransition() const {
 }
 
 PropertyValue<float> RasterLayer::getDefaultRasterFadeDuration() {
-    return { 300 };
+    return {300};
 }
 
 const PropertyValue<float>& RasterLayer::getRasterFadeDuration() const {
@@ -172,7 +172,7 @@ TransitionOptions RasterLayer::getRasterFadeDurationTransition() const {
 }
 
 PropertyValue<float> RasterLayer::getDefaultRasterHueRotate() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& RasterLayer::getRasterHueRotate() const {
@@ -199,7 +199,7 @@ TransitionOptions RasterLayer::getRasterHueRotateTransition() const {
 }
 
 PropertyValue<float> RasterLayer::getDefaultRasterOpacity() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& RasterLayer::getRasterOpacity() const {
@@ -226,7 +226,7 @@ TransitionOptions RasterLayer::getRasterOpacityTransition() const {
 }
 
 PropertyValue<RasterResamplingType> RasterLayer::getDefaultRasterResampling() {
-    return { RasterResamplingType::Linear };
+    return {RasterResamplingType::Linear};
 }
 
 const PropertyValue<RasterResamplingType>& RasterLayer::getRasterResampling() const {
@@ -253,7 +253,7 @@ TransitionOptions RasterLayer::getRasterResamplingTransition() const {
 }
 
 PropertyValue<float> RasterLayer::getDefaultRasterSaturation() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& RasterLayer::getRasterSaturation() const {
@@ -383,7 +383,8 @@ optional<Error> RasterLayer::setPaintProperty(const std::string& name, const Con
     
     if (property == Property::RasterResampling) {
         Error error;
-        optional<PropertyValue<RasterResamplingType>> typedValue = convert<PropertyValue<RasterResamplingType>>(value, error, false, false);
+        optional<PropertyValue<RasterResamplingType>> typedValue =
+            convert<PropertyValue<RasterResamplingType>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
diff --git a/src/mbgl/style/layers/symbol_layer.cpp b/src/mbgl/style/layers/symbol_layer.cpp
index b3ee0f698c..1383293d6d 100644
--- a/src/mbgl/style/layers/symbol_layer.cpp
+++ b/src/mbgl/style/layers/symbol_layer.cpp
@@ -109,15 +109,15 @@ void SymbolLayer::setIconIgnorePlacement(const PropertyValue<bool>& value) {
     baseImpl = std::move(impl_);
     observer->onLayerChanged(*this);
 }
-PropertyValue<std::string> SymbolLayer::getDefaultIconImage() {
+PropertyValue<expression::Image> SymbolLayer::getDefaultIconImage() {
     return IconImage::defaultValue();
 }
 
-const PropertyValue<std::string>& SymbolLayer::getIconImage() const {
+const PropertyValue<expression::Image>& SymbolLayer::getIconImage() const {
     return impl().layout.get<IconImage>();
 }
 
-void SymbolLayer::setIconImage(const PropertyValue<std::string>& value) {
+void SymbolLayer::setIconImage(const PropertyValue<expression::Image>& value) {
     if (value == getIconImage())
         return;
     auto impl_ = mutableImpl();
@@ -721,7 +721,7 @@ void SymbolLayer::setTextWritingMode(const PropertyValue<std::vector<TextWriting
 // Paint properties
 
 PropertyValue<Color> SymbolLayer::getDefaultIconColor() {
-    return { Color::black() };
+    return {Color::black()};
 }
 
 const PropertyValue<Color>& SymbolLayer::getIconColor() const {
@@ -748,7 +748,7 @@ TransitionOptions SymbolLayer::getIconColorTransition() const {
 }
 
 PropertyValue<float> SymbolLayer::getDefaultIconHaloBlur() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& SymbolLayer::getIconHaloBlur() const {
@@ -775,7 +775,7 @@ TransitionOptions SymbolLayer::getIconHaloBlurTransition() const {
 }
 
 PropertyValue<Color> SymbolLayer::getDefaultIconHaloColor() {
-    return { {} };
+    return {{}};
 }
 
 const PropertyValue<Color>& SymbolLayer::getIconHaloColor() const {
@@ -802,7 +802,7 @@ TransitionOptions SymbolLayer::getIconHaloColorTransition() const {
 }
 
 PropertyValue<float> SymbolLayer::getDefaultIconHaloWidth() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& SymbolLayer::getIconHaloWidth() const {
@@ -829,7 +829,7 @@ TransitionOptions SymbolLayer::getIconHaloWidthTransition() const {
 }
 
 PropertyValue<float> SymbolLayer::getDefaultIconOpacity() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& SymbolLayer::getIconOpacity() const {
@@ -856,7 +856,7 @@ TransitionOptions SymbolLayer::getIconOpacityTransition() const {
 }
 
 PropertyValue<std::array<float, 2>> SymbolLayer::getDefaultIconTranslate() {
-    return { {{ 0, 0 }} };
+    return {{{0, 0}}};
 }
 
 const PropertyValue<std::array<float, 2>>& SymbolLayer::getIconTranslate() const {
@@ -883,7 +883,7 @@ TransitionOptions SymbolLayer::getIconTranslateTransition() const {
 }
 
 PropertyValue<TranslateAnchorType> SymbolLayer::getDefaultIconTranslateAnchor() {
-    return { TranslateAnchorType::Map };
+    return {TranslateAnchorType::Map};
 }
 
 const PropertyValue<TranslateAnchorType>& SymbolLayer::getIconTranslateAnchor() const {
@@ -910,7 +910,7 @@ TransitionOptions SymbolLayer::getIconTranslateAnchorTransition() const {
 }
 
 PropertyValue<Color> SymbolLayer::getDefaultTextColor() {
-    return { Color::black() };
+    return {Color::black()};
 }
 
 const PropertyValue<Color>& SymbolLayer::getTextColor() const {
@@ -937,7 +937,7 @@ TransitionOptions SymbolLayer::getTextColorTransition() const {
 }
 
 PropertyValue<float> SymbolLayer::getDefaultTextHaloBlur() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& SymbolLayer::getTextHaloBlur() const {
@@ -964,7 +964,7 @@ TransitionOptions SymbolLayer::getTextHaloBlurTransition() const {
 }
 
 PropertyValue<Color> SymbolLayer::getDefaultTextHaloColor() {
-    return { {} };
+    return {{}};
 }
 
 const PropertyValue<Color>& SymbolLayer::getTextHaloColor() const {
@@ -991,7 +991,7 @@ TransitionOptions SymbolLayer::getTextHaloColorTransition() const {
 }
 
 PropertyValue<float> SymbolLayer::getDefaultTextHaloWidth() {
-    return { 0 };
+    return {0};
 }
 
 const PropertyValue<float>& SymbolLayer::getTextHaloWidth() const {
@@ -1018,7 +1018,7 @@ TransitionOptions SymbolLayer::getTextHaloWidthTransition() const {
 }
 
 PropertyValue<float> SymbolLayer::getDefaultTextOpacity() {
-    return { 1 };
+    return {1};
 }
 
 const PropertyValue<float>& SymbolLayer::getTextOpacity() const {
@@ -1045,7 +1045,7 @@ TransitionOptions SymbolLayer::getTextOpacityTransition() const {
 }
 
 PropertyValue<std::array<float, 2>> SymbolLayer::getDefaultTextTranslate() {
-    return { {{ 0, 0 }} };
+    return {{{0, 0}}};
 }
 
 const PropertyValue<std::array<float, 2>>& SymbolLayer::getTextTranslate() const {
@@ -1072,7 +1072,7 @@ TransitionOptions SymbolLayer::getTextTranslateTransition() const {
 }
 
 PropertyValue<TranslateAnchorType> SymbolLayer::getDefaultTextTranslateAnchor() {
-    return { TranslateAnchorType::Map };
+    return {TranslateAnchorType::Map};
 }
 
 const PropertyValue<TranslateAnchorType>& SymbolLayer::getTextTranslateAnchor() const {
@@ -1332,7 +1332,8 @@ optional<Error> SymbolLayer::setPaintProperty(const std::string& name, const Con
     
     if (property == Property::IconTranslate || property == Property::TextTranslate) {
         Error error;
-        optional<PropertyValue<std::array<float, 2>>> typedValue = convert<PropertyValue<std::array<float, 2>>>(value, error, false, false);
+        optional<PropertyValue<std::array<float, 2>>> typedValue =
+            convert<PropertyValue<std::array<float, 2>>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -1351,7 +1352,8 @@ optional<Error> SymbolLayer::setPaintProperty(const std::string& name, const Con
     
     if (property == Property::IconTranslateAnchor || property == Property::TextTranslateAnchor) {
         Error error;
-        optional<PropertyValue<TranslateAnchorType>> typedValue = convert<PropertyValue<TranslateAnchorType>>(value, error, false, false);
+        optional<PropertyValue<TranslateAnchorType>> typedValue =
+            convert<PropertyValue<TranslateAnchorType>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -1665,7 +1667,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::IconAnchor || property == Property::TextAnchor) {
         Error error;
-        optional<PropertyValue<SymbolAnchorType>> typedValue = convert<PropertyValue<SymbolAnchorType>>(value, error, true, false);
+        optional<PropertyValue<SymbolAnchorType>> typedValue =
+            convert<PropertyValue<SymbolAnchorType>>(value, error, true, false);
         if (!typedValue) {
             return error;
         }
@@ -1684,7 +1687,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::IconImage) {
         Error error;
-        optional<PropertyValue<std::string>> typedValue = convert<PropertyValue<std::string>>(value, error, true, true);
+        optional<PropertyValue<expression::Image>> typedValue =
+            convert<PropertyValue<expression::Image>>(value, error, true, true);
         if (!typedValue) {
             return error;
         }
@@ -1696,7 +1700,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::IconOffset || property == Property::TextOffset) {
         Error error;
-        optional<PropertyValue<std::array<float, 2>>> typedValue = convert<PropertyValue<std::array<float, 2>>>(value, error, true, false);
+        optional<PropertyValue<std::array<float, 2>>> typedValue =
+            convert<PropertyValue<std::array<float, 2>>>(value, error, true, false);
         if (!typedValue) {
             return error;
         }
@@ -1827,7 +1832,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::IconTextFit) {
         Error error;
-        optional<PropertyValue<IconTextFitType>> typedValue = convert<PropertyValue<IconTextFitType>>(value, error, false, false);
+        optional<PropertyValue<IconTextFitType>> typedValue =
+            convert<PropertyValue<IconTextFitType>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -1839,7 +1845,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::IconTextFitPadding) {
         Error error;
-        optional<PropertyValue<std::array<float, 4>>> typedValue = convert<PropertyValue<std::array<float, 4>>>(value, error, false, false);
+        optional<PropertyValue<std::array<float, 4>>> typedValue =
+            convert<PropertyValue<std::array<float, 4>>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -1851,7 +1858,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::SymbolPlacement) {
         Error error;
-        optional<PropertyValue<SymbolPlacementType>> typedValue = convert<PropertyValue<SymbolPlacementType>>(value, error, false, false);
+        optional<PropertyValue<SymbolPlacementType>> typedValue =
+            convert<PropertyValue<SymbolPlacementType>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -1863,7 +1871,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::SymbolZOrder) {
         Error error;
-        optional<PropertyValue<SymbolZOrderType>> typedValue = convert<PropertyValue<SymbolZOrderType>>(value, error, false, false);
+        optional<PropertyValue<SymbolZOrderType>> typedValue =
+            convert<PropertyValue<SymbolZOrderType>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -1875,7 +1884,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::TextField) {
         Error error;
-        optional<PropertyValue<expression::Formatted>> typedValue = convert<PropertyValue<expression::Formatted>>(value, error, true, true);
+        optional<PropertyValue<expression::Formatted>> typedValue =
+            convert<PropertyValue<expression::Formatted>>(value, error, true, true);
         if (!typedValue) {
             return error;
         }
@@ -1887,7 +1897,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::TextFont) {
         Error error;
-        optional<PropertyValue<std::vector<std::string>>> typedValue = convert<PropertyValue<std::vector<std::string>>>(value, error, true, false);
+        optional<PropertyValue<std::vector<std::string>>> typedValue =
+            convert<PropertyValue<std::vector<std::string>>>(value, error, true, false);
         if (!typedValue) {
             return error;
         }
@@ -1911,7 +1922,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::TextTransform) {
         Error error;
-        optional<PropertyValue<TextTransformType>> typedValue = convert<PropertyValue<TextTransformType>>(value, error, true, false);
+        optional<PropertyValue<TextTransformType>> typedValue =
+            convert<PropertyValue<TextTransformType>>(value, error, true, false);
         if (!typedValue) {
             return error;
         }
@@ -1923,7 +1935,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::TextVariableAnchor) {
         Error error;
-        optional<PropertyValue<std::vector<TextVariableAnchorType>>> typedValue = convert<PropertyValue<std::vector<TextVariableAnchorType>>>(value, error, false, false);
+        optional<PropertyValue<std::vector<TextVariableAnchorType>>> typedValue =
+            convert<PropertyValue<std::vector<TextVariableAnchorType>>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
@@ -1935,7 +1948,8 @@ optional<Error> SymbolLayer::setLayoutProperty(const std::string& name, const Co
     
     if (property == Property::TextWritingMode) {
         Error error;
-        optional<PropertyValue<std::vector<TextWritingModeType>>> typedValue = convert<PropertyValue<std::vector<TextWritingModeType>>>(value, error, false, false);
+        optional<PropertyValue<std::vector<TextWritingModeType>>> typedValue =
+            convert<PropertyValue<std::vector<TextWritingModeType>>>(value, error, false, false);
         if (!typedValue) {
             return error;
         }
diff --git a/src/mbgl/style/layers/symbol_layer_properties.hpp b/src/mbgl/style/layers/symbol_layer_properties.hpp
index e44e7e404f..6552589971 100644
--- a/src/mbgl/style/layers/symbol_layer_properties.hpp
+++ b/src/mbgl/style/layers/symbol_layer_properties.hpp
@@ -31,9 +31,9 @@ struct IconIgnorePlacement : LayoutProperty<bool> {
     static bool defaultValue() { return false; }
 };
 
-struct IconImage : DataDrivenLayoutProperty<std::string> {
+struct IconImage : DataDrivenLayoutProperty<expression::Image> {
     static constexpr const char *name() { return "icon-image"; }
-    static std::string defaultValue() { return ""; }
+    static expression::Image defaultValue() { return {}; }
 };
 
 struct IconKeepUpright : LayoutProperty<bool> {
@@ -43,7 +43,7 @@ struct IconKeepUpright : LayoutProperty<bool> {
 
 struct IconOffset : DataDrivenLayoutProperty<std::array<float, 2>> {
     static constexpr const char *name() { return "icon-offset"; }
-    static std::array<float, 2> defaultValue() { return {{ 0, 0 }}; }
+    static std::array<float, 2> defaultValue() { return {{0, 0}}; }
 };
 
 struct IconOptional : LayoutProperty<bool> {
@@ -83,7 +83,7 @@ struct IconTextFit : LayoutProperty<IconTextFitType> {
 
 struct IconTextFitPadding : LayoutProperty<std::array<float, 4>> {
     static constexpr const char *name() { return "icon-text-fit-padding"; }
-    static std::array<float, 4> defaultValue() { return {{ 0, 0, 0, 0 }}; }
+    static std::array<float, 4> defaultValue() { return {{0, 0, 0, 0}}; }
 };
 
 struct SymbolAvoidEdges : LayoutProperty<bool> {
@@ -123,12 +123,12 @@ struct TextAnchor : DataDrivenLayoutProperty<SymbolAnchorType> {
 
 struct TextField : DataDrivenLayoutProperty<expression::Formatted> {
     static constexpr const char *name() { return "text-field"; }
-    static expression::Formatted defaultValue() { return ""; }
+    static expression::Formatted defaultValue() { return {}; }
 };
 
 struct TextFont : DataDrivenLayoutProperty<std::vector<std::string>> {
     static constexpr const char *name() { return "text-font"; }
-    static std::vector<std::string> defaultValue() { return { "Open Sans Regular", "Arial Unicode MS Regular" }; }
+    static std::vector<std::string> defaultValue() { return {{"Open Sans Regular"}, {"Arial Unicode MS Regular"}}; }
 };
 
 struct TextIgnorePlacement : LayoutProperty<bool> {
@@ -168,7 +168,7 @@ struct TextMaxWidth : DataDrivenLayoutProperty<float> {
 
 struct TextOffset : DataDrivenLayoutProperty<std::array<float, 2>> {
     static constexpr const char *name() { return "text-offset"; }
-    static std::array<float, 2> defaultValue() { return {{ 0, 0 }}; }
+    static std::array<float, 2> defaultValue() { return {{0, 0}}; }
 };
 
 struct TextOptional : LayoutProperty<bool> {
@@ -213,12 +213,12 @@ struct TextTransform : DataDrivenLayoutProperty<TextTransformType> {
 
 struct TextVariableAnchor : LayoutProperty<std::vector<TextVariableAnchorType>> {
     static constexpr const char *name() { return "text-variable-anchor"; }
-    static std::vector<TextVariableAnchorType> defaultValue() { return {  }; }
+    static std::vector<TextVariableAnchorType> defaultValue() { return {}; }
 };
 
 struct TextWritingMode : LayoutProperty<std::vector<TextWritingModeType>> {
     static constexpr const char *name() { return "text-writing-mode"; }
-    static std::vector<TextWritingModeType> defaultValue() { return {  }; }
+    static std::vector<TextWritingModeType> defaultValue() { return {}; }
 };
 
 struct IconColor : DataDrivenPaintProperty<Color, attributes::fill_color, uniforms::fill_color> {
@@ -242,7 +242,7 @@ struct IconOpacity : DataDrivenPaintProperty<float, attributes::opacity, uniform
 };
 
 struct IconTranslate : PaintProperty<std::array<float, 2>> {
-    static std::array<float, 2> defaultValue() { return {{ 0, 0 }}; }
+    static std::array<float, 2> defaultValue() { return {{0, 0}}; }
 };
 
 struct IconTranslateAnchor : PaintProperty<TranslateAnchorType> {
@@ -273,7 +273,7 @@ struct TextOpacity : DataDrivenPaintProperty<float, attributes::opacity, uniform
 };
 
 struct TextTranslate : PaintProperty<std::array<float, 2>> {
-    static std::array<float, 2> defaultValue() { return {{ 0, 0 }}; }
+    static std::array<float, 2> defaultValue() { return {{0, 0}}; }
 };
 
 struct TextTranslateAnchor : PaintProperty<TranslateAnchorType> {