5 files changed, 45 insertions, 7 deletions

diff --git a/src/mbgl/style/layers/circle_layer.cpp b/src/mbgl/style/layers/circle_layer.cpp
index ad34ba8223..bf415ea42d 100644
--- a/src/mbgl/style/layers/circle_layer.cpp
+++ b/src/mbgl/style/layers/circle_layer.cpp
@@ -24,7 +24,7 @@ const LayerTypeInfo* CircleLayer::Impl::staticTypeInfo() noexcept {
     const static LayerTypeInfo typeInfo{"circle",
                                         LayerTypeInfo::Source::Required,
                                         LayerTypeInfo::Pass3D::NotRequired,
-                                        LayerTypeInfo::Layout::NotRequired,
+                                        LayerTypeInfo::Layout::Required,
                                         LayerTypeInfo::FadingTiles::NotRequired,
                                         LayerTypeInfo::CrossTileIndex::NotRequired,
                                         LayerTypeInfo::TileKind::Geometry};
@@ -57,11 +57,27 @@ std::unique_ptr<Layer> CircleLayer::cloneRef(const std::string& id_) const {
     return std::make_unique<CircleLayer>(std::move(impl_));
 }
 
-void CircleLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>&) const {
+void CircleLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>& writer) const {
+    layout.stringify(writer);
 }
 
 // Layout properties
 
+PropertyValue<float> CircleLayer::getDefaultCircleSortKey() {
+    return CircleSortKey::defaultValue();
+}
+
+const PropertyValue<float>& CircleLayer::getCircleSortKey() const {
+    return impl().layout.get<CircleSortKey>();
+}
+
+void CircleLayer::setCircleSortKey(const PropertyValue<float>& value) {
+    if (value == getCircleSortKey()) return;
+    auto impl_ = mutableImpl();
+    impl_->layout.get<CircleSortKey>() = value;
+    baseImpl = std::move(impl_);
+    observer->onLayerChanged(*this);
+}
 
 // Paint properties
 
@@ -391,6 +407,7 @@ enum class Property : uint8_t {
     CircleStrokeWidthTransition,
     CircleTranslateTransition,
     CircleTranslateAnchorTransition,
+    CircleSortKey = kPaintPropertyCount,
 };
 
 template <typename T>
@@ -420,7 +437,8 @@ MAPBOX_ETERNAL_CONSTEXPR const auto layerProperties = mapbox::eternal::hash_map<
      {"circle-stroke-opacity-transition", toUint8(Property::CircleStrokeOpacityTransition)},
      {"circle-stroke-width-transition", toUint8(Property::CircleStrokeWidthTransition)},
      {"circle-translate-transition", toUint8(Property::CircleTranslateTransition)},
-     {"circle-translate-anchor-transition", toUint8(Property::CircleTranslateAnchorTransition)}});
+     {"circle-translate-anchor-transition", toUint8(Property::CircleTranslateAnchorTransition)},
+     {"circle-sort-key", toUint8(Property::CircleSortKey)}});
 
 StyleProperty getLayerProperty(const CircleLayer& layer, Property property) {
     switch (property) {
@@ -468,6 +486,8 @@ StyleProperty getLayerProperty(const CircleLayer& layer, Property property) {
             return makeStyleProperty(layer.getCircleTranslateTransition());
         case Property::CircleTranslateAnchorTransition:
             return makeStyleProperty(layer.getCircleTranslateAnchorTransition());
+        case Property::CircleSortKey:
+            return makeStyleProperty(layer.getCircleSortKey());
     }
     return {};
 }
@@ -500,7 +520,8 @@ optional<Error> CircleLayer::setPropertyInternal(const std::string& name, const
     auto property = static_cast<Property>(it->second);
 
     if (property == Property::CircleBlur || property == Property::CircleOpacity || property == Property::CircleRadius ||
-        property == Property::CircleStrokeOpacity || property == Property::CircleStrokeWidth) {
+        property == Property::CircleStrokeOpacity || property == Property::CircleStrokeWidth ||
+        property == Property::CircleSortKey) {
         Error error;
         const auto& typedValue = convert<PropertyValue<float>>(value, error, true, false);
         if (!typedValue) {
@@ -531,6 +552,11 @@ optional<Error> CircleLayer::setPropertyInternal(const std::string& name, const
             setCircleStrokeWidth(*typedValue);
             return nullopt;
         }
+
+        if (property == Property::CircleSortKey) {
+            setCircleSortKey(*typedValue);
+            return nullopt;
+        }
     }
     if (property == Property::CircleColor || property == Property::CircleStrokeColor) {
         Error error;
diff --git a/src/mbgl/style/layers/circle_layer_impl.cpp b/src/mbgl/style/layers/circle_layer_impl.cpp
index bf0688ac8b..d40cc4bf9a 100644
--- a/src/mbgl/style/layers/circle_layer_impl.cpp
+++ b/src/mbgl/style/layers/circle_layer_impl.cpp
@@ -6,8 +6,7 @@ namespace style {
 bool CircleLayer::Impl::hasLayoutDifference(const Layer::Impl& other) const {
     assert(other.getTypeInfo() == getTypeInfo());
     const auto& impl = static_cast<const style::CircleLayer::Impl&>(other);
-    return filter     != impl.filter ||
-           visibility != impl.visibility ||
+    return filter != impl.filter || visibility != impl.visibility || layout != impl.layout ||
            paint.hasDataDrivenPropertyDifference(impl.paint);
 }
 
diff --git a/src/mbgl/style/layers/circle_layer_impl.hpp b/src/mbgl/style/layers/circle_layer_impl.hpp
index 9b3ce48706..4826e58a63 100644
--- a/src/mbgl/style/layers/circle_layer_impl.hpp
+++ b/src/mbgl/style/layers/circle_layer_impl.hpp
@@ -14,6 +14,7 @@ public:
     bool hasLayoutDifference(const Layer::Impl&) const override;
     void stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>&) const override;
 
+    CircleLayoutProperties::Unevaluated layout;
     CirclePaintProperties::Transitionable paint;
 
     DECLARE_LAYER_TYPE_INFO;
diff --git a/src/mbgl/style/layers/circle_layer_properties.hpp b/src/mbgl/style/layers/circle_layer_properties.hpp
index 5204421d0b..c8ec81eed5 100644
--- a/src/mbgl/style/layers/circle_layer_properties.hpp
+++ b/src/mbgl/style/layers/circle_layer_properties.hpp
@@ -16,6 +16,11 @@
 namespace mbgl {
 namespace style {
 
+struct CircleSortKey : DataDrivenLayoutProperty<float> {
+    static constexpr const char *name() { return "circle-sort-key"; }
+    static float defaultValue() { return 0; }
+};
+
 struct CircleBlur : DataDrivenPaintProperty<float, attributes::blur, uniforms::blur> {
     static float defaultValue() { return 0; }
 };
@@ -60,6 +65,10 @@ struct CircleTranslateAnchor : PaintProperty<TranslateAnchorType> {
     static TranslateAnchorType defaultValue() { return TranslateAnchorType::Map; }
 };
 
+class CircleLayoutProperties : public Properties<
+    CircleSortKey
+> {};
+
 class CirclePaintProperties : public Properties<
     CircleBlur,
     CircleColor,
diff --git a/src/mbgl/style/layers/layer.cpp.ejs b/src/mbgl/style/layers/layer.cpp.ejs
index fd5bf619f7..8fd4b1fef0 100644
--- a/src/mbgl/style/layers/layer.cpp.ejs
+++ b/src/mbgl/style/layers/layer.cpp.ejs
@@ -73,7 +73,10 @@ layerCapabilities['symbol']         = defaults.require('Source')
                                               .require('CrossTileIndex')
                                               .set('TileKind', 'Geometry')
                                               .finalize();
-layerCapabilities['circle']         = defaults.require('Source').set('TileKind', 'Geometry').finalize();
+layerCapabilities['circle']         = defaults.require('Source')
+                                              .require('Layout')
+                                              .set('TileKind', 'Geometry')
+                                              .finalize();
 layerCapabilities['line']           = layerCapabilities['fill'];
 layerCapabilities['heatmap']        = defaults.require('Source')
                                               .require('Pass3D')